Since my experience was from a number of years back, I tried searching for more recent reports: "mysql ssd fsync performance". The top recent one I found was for Digital Ocean[0] in 2020. It says "average of about 20ms which matches your 50/sec" and mentions battery back-up controllers which wasn't even in my search terms.

[0] https://www.digitalocean.com/community/questions/poor-fsync-...