Yup, mentioned it back in the tech layoffs thread. It's not uncommon at all and I even have direct experience in this regard, both as a STEM grad and knowing other STEM majors personally.
My brother has a degree in Math from a top STEM school in Cali (and served in the military) but does sales.
My brother's friend has a Physics degree from UCLA and has been doing a bartending job for the last 10 years.
A lot of my classmates I went to school with don't work in STEM.
A lot more are doing basic spreadsheet/data entry work, far away from their degree.
I'm actually back in school right now finishing an EE degree and many EE's from my class already feel like they're not going to get a job in this field either. They can't even get an internship. The software company I work for right told me I can't even change over to hardware because they got no room (and even laid off recently from the department).
There are simply too few positions and a lot of seniority locking it out. Basically take whatever job you can get but keep applying to your field. It is a thing though that if you graduate but can't find work in your field after 2-3 years, a lot of employers see you as "past it". Chances are you'll settle doing something else because you couldn't get established your first year after graduating.
Not to mention, some salaries are a joke and have not scaled. Entry-level Mechanical Engineers back in the early 2000's made $65k-$70k when $100k was a lot of money. Now the $100k equivalent to that time is ~$173k due to inflation and high costs, yet the average entry Mechanical Engineer salary is still around $80k $70k. The pay-off ain't the same, probably because every year there are 50k more ME grads from the U.S alone, but not 50k more job openings.
The software boom where the salaries went nuclear masked this problem. Many people saw the salaries and pursued that path, however now we're returning back to the floor as jobs from that sector are running into the traditional STEM career-issues from the 2000's: seniority locking jobs up along with more and more graduates but not enough jobs to go around, increased rates, etc.
Like the 2nd to last slide also mentions, many of these STEM jobs simply don't create a lot of value or end up producing harmful effects (basically the opposite of what students studied). That drains some of the smarter graduates who pursued this path due to strong ideals, like saving the world. They realize so much of it is CEO's trying to convince other people they need a product, cutting corners, producing a shytty one and cashing out. Basically ponzi after ponzi. Most CEO's just wants to make money, they don't care about anything else.
For some of the legit jobs, as mentioned earlier: a lot of these jobs aren't easy. It's a lot of hours worked and the pay doesn't justify some of them. A lot of people who went in for the money realized there isn't money and they don't like what they're doing so why stay in the industry? The people who are in it for the love of it are many times the only ones around. Some of those people will work those jobs for the bare minimum and these CEO's know it.
At the end of the day though, regardless of all these factors: this means a higher bar of entry to many jobs around the country. Yes, it's "funny" that STEM grads aren't working STEM jobs, but that means they're going for the other jobs. You may laugh at them for their struggles, but you'll be competing with an Aerospace Engineer graduate for a decent paying desk job - because as of the middle of last year Boeing has been on a hiring freeze (that's actually real news). Going STEM is still one of the best options right now, even if you don't work in those fields you'll hold a favorable advantage for non-manual labor jobs. Additionally, when older engineers start retiring or get close to it a lot of positions start opening up.