Yes, that’s clearly GitHub looking at the contents. At that point you just have to trust they don’t do anything else with the internal representation they’ve built.

When Gmail was introduced two decades ago, there was some short-lived furore about the fact that Google admitted they were reading your emails for ad targeting purposes. To a lot of people like myself, this seemed a bridge too far when you’re used to servers that don’t “look” at your private stuff. But it certainly didn’t hurt Gmail’s adoption. (I still don’t use Gmail because of this original lingering distaste.)