He's correct...the National Geographic article and the Britannica articles are misinformation (the author of the Britannica article is not a historian of Africa but instead just some person with a degree in music), as are most of the claims in Mrs. Farmer-Paellman's statements, her lawsuit, and the claims of one of the professors (Seck) she got to respond to her inquiries.
I can provide a more detailed explanation later, if you can wait a few days...for now, please read the Wikipedia talk page on the Kingdom of Benin (
Talk:Kingdom of Benin - Wikipedia) where some of the things being discussed in the thread have already been partially addressed...including the (incorrect and misleading) article on researchgate by Dmitri Bondarenko that you quoted from. There is more to say on this, but it would take a while to write up.