You’ve clearly never interacted with a regulator before. When a regulator send you a letter with difficult questions, there is an extremely strong implication that a failure to answer those questions correctly will lead to more difficult questions, and, undoubtedly, official investigations.

You don’t want an official investigation, they are a complete nightmare that eat up months of work hours. Much better to spend a couple of days making sure you can give the correct answers on the first pass. Unless of course you genuinely believe the regulators are pushing beyond their remit, but know you’re voluntary signing up for an expensive and protracted fight.

It is incredibly naive to suggest that someone with that power "sending a letter asking questions" would be remotely similar to you or I doing the same.

The EU has an long tradition of "conversations" and "questions" with an unstated "give the right answer and you can avoid an unpleasant official action".

You're right there is no official casework. That is also entirely irrelevant to the issue of whether or not Apple caved under pressure.

_Most_ regulatory enforcement, in practice, is “letters asking questions”. The formal cases you see are generally where the response to the letters was unsatisfactory.

(In some cases this is itself somewhat formalised.)