> I'm going to be the nerd that points out that it has not been mathematically proven that pi contains every substring

Fascinating. Do you know if this has been proven about any interesting number (that wasn't explicitly constructed to make this true)?

https://en.wikipedia.org/wiki/Normal_number has some examples and a bunch of info. Most of them are pretty artificial, but the concatenation of the primes one is... at least interesting, not obvious (to me) from doing that that it'd be normal.