yes

https://docs.invidious.io/

https://api.invidious.io/

Yes. Exactly.

Does it strip ads?

Yes, and it supports Sponsor Block, to skip promotions built into the videos, like those annoying VPN sponsorships.

Well that explains it doesn't it?

I don't think anyone is at a loss for an explanation at this point. The discussion is more around condemnation.

It only loads the video and related information, if that's what you mean.

It is really YouTube's own fault for not securely embedding the ads into the videos.