I think they do, maybe a little later _after_ the release: https://support.apple.com/en-gb/HT201222

Which might make sense if it is security updates.

By the way, is this violate any laws anywhere?

I'd be curious too. Are there any laws that say "if you provide software to which the user agrees to use, and you later change it, you must disclose what the changes are"?

iOS presents the entire ToS when you update to a new major version, so clearly you are agreeing to something when you accept the update. But what about the small updates?