Is there "benchmark data" on different memory techniques? I also wondered about this because I also memorized 50 digits on a lark back in high school, without the post's encoding technique and memory palace.

I added one block of 10 digits per night, spending maybe 10 minutes per night? Very roughly an hour total, ~same as the poster spent to get 100 digits, but without the prior investment they spent on the PAO (memorizing 300 key-value pairs, apparently).

You'd want to compare to Anki, too.