There are many cited sources, such as this one: https://www.theregister.com/2021/08/13/amazon_game_contracts... but this was just a single case, retracted for bad publicity.

They try their shenigans even in Germany. You need to get all your private work approved by a committee, otherwise you are not allowed to maintain it off-work, because it may conflict with Amazon business interests. Try that with your 300 repos. You might get 2-4 approved, after months.

And they really believe their intellectual properties trump your intellectual property, not vice versa. You'll learn from them, not them from you. Ha