This is what worries me a bit, that this will be used as an excuse for walled gardens and so forth.

"We can't allow side loading because that would be illegal in terms of age verification".

I would love to be wrong about this though.

It's always possible that they'll say it, but it would be a lie based on my reading of this bill. Sideloaded apps can choose whether or not to respect the OS's advice about the age of the user, it's not on the OS or device to enforce them being honest.

It's beyond obvious that it will, and it's why Google and Apple support it