Just as a point of technicality, this is not pro rata for YC, right?

> a pro rata clause in an investment agreement gives the investor a right (but not the obligation) to participate in one or more future financing rounds to maintain their percentage stake in the company.

This deal explicitly says "hey, here's 375k; we'll take whatever share of your company that is next time you raise." That's not maintaining percentage stake; it's actually agreeing to the possibility of a fairly small stake.