If Apple wants to be on the EU market they will have to comply with EU regulations, and if regulations are lacking regulators will regulate.
Whether you suck up to Apple or the EU is your opinion. I live in EU and I'm happy to see the otherwise sparsely regulated megacorporations from USA be regulated to not exploit my fellow union citizens.
Apple has also shown repeatedly that they're unwilling to comply by implementing their own shitty interpretation of our rules (ship a fucking USB-C adapter with your phone when we're demanding USB-C in the device, this markets act notarizaton and "core fee" bullshit).
I don't know if developers are still not allowed to advertise alternative payment methods, but it's just one step too far.
This is moving the goalposts. Both my comment and the comment you first replied to was making normative statements about government policy, not questioning whether they have the authority to make such laws.
"Pretty outrageous" is good enough for me, if Microsoft tried to start charging for access to Win32 it would not succeed in any way, legal or with customers (it would be abusing market power), but because Apple has a strong hold on their users already they're supposed to just fall over and be fucked by fees that completely ruin any kind of "not very monetizeable" app because of their made up business rules? Markets are regulated everywhere, why should Apple be treated differently because they started from a different position?
You can spare me the reply
"sounds outrageous" is a pretty weak justification for regulator action. Paying for a browser probably sounds equally as outrageous, but with the way anti-trust is going with Chrome/Google, that seems like a very real possibility. Moreover, why should the government should be in the basis of regulating business models? If Apple wants to charge for access to its SDKs, and it pays the price through less apps for its users, so be it.