I've used this from the start. Btw you don't need to give your google account to use this in any way. It is a fully functional (better) youtube client.

Been using it for a while now and there's no need to log in with your account - in fact, you can't! You have to import subscriptions over, and easy to follow instructions to do this are provided. The only thing you can't to is comment, but for the few times I actually want to comment, its no hassle to go to the mobile website.

My only major complaint is that the colour of the seek bar is hard to see on black backgrounds.

It was a fake story in a Github issue.

I've been using it on my Android phone for over 3 years, while always being signed into Google. Never had any issues.