Good idea. It's an interesting historical question - when we picked 4.0 as the default ~25 years ago, how close was is to the calculated value? I was asking that myself. Unfortunately I don't have a machine with traditional HDD in my homelab anymore, but I'll see if I can run the test somewhere.

I wouldn't be all that surprised if this was (partially) due to Postgres being less optimized back then, which might have hidden some of the random vs. sequential differences. But that's just a wild guess.