Agree, YC is a company. Instead of owning 100% of IP and products being developed, it owns 7% of it. More thoughts here (from 2016): [0], also in comparison to Alphabet.
Rather a platform, isn't it? Matches founders with VC for a stake of 7% as fee.
Platforms thrive if you match supply and demand in a highly relevant way, and once they thrive, they generate network effects.
So PG & Jessica were sort of the equivalent of the seller terms and conditions on the Amazon marketplace platform haha. They were able to spot and shape promising founding teams.
[0]: https://medium.com/simone-brunozzi/y-combinator-and-alphabet...