Do you automatically get removed from GAs for games you just won?

Yup. It's been like that for a while.

Yes. It wasn't like that before, but cg added the feature like a year ago I believe.

https://www.steamgifts.com/about/faq

"You win a game while having other active giveaway entries for that same game. In this case the site will automatically remove those entries to prevent the possibility of you winning the game twice, and the points will be refunded."

It works mostly but not every time.

I think the problems are with the "steam learning" GA's but haven't checked it closer because it dont happen often that the entries are not removed.