You're correct.
Tracing African Roots does great break downs. Benin/Togo can also be proxies for Nigerian or Ghanaian ancestry for example. Ghana can be a proxy for Liberian or Burkinabe ancestry as well.
i also wouldn't downplay Nigerian ancestry in African Americans (or any Afro-diasporic group really),
Nigerian groups such as the Igbo, with documented histories of those groups being prominent in different parts of the South (particularly Virginia).
I think the Nigerian DNA is grossly overstated in African Americans by these DNA companies and at this point those companies are basically engaging in confirmation bias, which is based upon them only going to Nigeria or Ghana to get samples and squeezing all of their customers into one of those two groups. Literally 559 of 23andme 717 samples from West Africa come from Ghana and Nigeria. I am not joking. It is right on their website:
West African
717
Nigerian
279
Nigerian, Yoruba, Esan
Ghanaian, Liberian & Sierra Leonean
280
Ivorian, Ghanaian, Liberian, Mende, Temne, Limba, Sierra Leonean
The other 158 samples covers a huge region from Senegal, Gambia and Guinea.
Senegambian & Guinean
158
Gambian, Guinean, Bissau-Guinean, Mandenka, Senegalese
There is nothing for Mali or Burkina Faso. So basically 23andme is using 717 samples as proxy for 400 million people in West Africa. Meanwhile they have over 1,000 samples for England by itself.
As bad as 23andme is; Ancestry.com is just a flat out joke at this point. I don't even know where they are getting their samples from, but their data is worse now then it was 10 years ago.
You should know that it is confirmation bias, because as I stated we don't even see any samples for places like Burkina Faso which was a major area that contributed slaves to the USA due to the annual tribute payments in slaves that the Dagomba people (and their relatives the Mamprussi and Mossi) had to pay to the Ashanti. There were also other groups there like the Hausa and various tribes from Niger and Ivory Coast that raided villages in Northern Ghana and Burkina Faso for people. That is why the modern governments of Ghana knows where many African Americans are from because they know who captured their ancestors and who sold them and they know who they sold those people to (the British).
I am inclined to believe that what these researchers are attributing as Nigerian DNA is likely from neighboring regions to the North and West (like Burkina Faso and Mali). The researchers are clearly just lumping them all together and calling it Nigeria, even though the people to the North and West were largely Fulani, Mande and Ga people that lived in and around Mali. If you a notice that in all of these updates as they get more samples from places like Togo and Benin; the Nigerian DNA is lessening in people and the Togo and Benin results are growing which shows that they are slowly getting more samples from the Northern and western regions. I am positive that if more samples are gotten from regions like Burkina Faso, Northern Ghana, Northern Ivory Coast, Mali and then areas along the rice coast; that we are going to see an even more dramatic shift for African Americans towards the West, especially if the samples come from Mande and Fulani groups in those regions.
On a side note if you look at charts of where people were brought from then you would see that Nigeria was not a major area for the USA, because initially America was growing specialized crops like rice. That meant that America would have to take slaves from specialized groups along the Rice Coast, which is that area a between Senegal to Liberia and over into neighboring Ivory Coast. Oddly enough that is exactly where slaving records stated that most of the slaves originated from specifically places like Sierra Leone, Liberia, Gambia, Guinea and Senegal. Congo was another area that they took quite a few slaves from, because they were mixing people in the USA to lessen the likelihood of slave revolts. In any event most African Americans ancestors came to the USA between 1720-1780. So the groups were already in place and historical records were very clear on that. To make things even clearer. The USA likely received only 4 percent of all slaves. So very few people actually came to the USA and then they basically stopped importing people from Africa in early 1800. Culturally it is pretty clear where African Americans are predominantly from, because they exhibit a blues based musical tradition and their Christian churches have very strong underlying Islamic influences which is what you would expect from people that lived along the Rice Coast in modern day Burkina Faso and Northern Ghana.
Some Nigerians did come to the USA, but not in nearly the numbers that people keep overstating. Most Nigerians were taken to the Caribbean and South America, which is shown by their cultural impact in places like Cuba. What we now call Nigeria did not enter wholesale slaving until after the mid to late 1700s mostly through the Oyo people, Aro Confederacy and the Islamic leader Usman Dan Fodio. Due to unreported slave revolts like the Stono Rebellion in South Carolina, the USA had by and large stop taking slaves directly from Africa when the Nigerians were just kicking into full drive. So Nigerian DNA results look to be grossly overstated in African American by 23andme and Ancestry.com. I have slowly come to the realization that African Ancestry results are probably the most accurate, simply because they have more samples. Like I stated I don't know if they can pinpoint a specific tribe within an ethnic group, but I think that they identify the correct overall ethnic group.