Except the type certificate issued by the FAA for a given aircraft is by definition the FAA saying that the type meets all applicable standards and is safe to fly. So is the granting of exceptions to any applicable requirements.
The FAA doesn’t say “eh maybe, it’s a judgement call” to an aircraft manufacturer when telling them whether or not the plane can board passengers. They may include various factors, probabilities, and judgement calls in their own determination of if the type gets certified or not, but ultimately there _is_ a determination made: either it can fly in a given context, or it cannot.
If the argument is “we learn and get better over time, and just because we approved something yesterday doesn’t mean we approve it today”, I fully agree with that, but within reason. And while I don’t agree with this mitigation being an acceptable exception, I also don’t think it’s “insane” or incredulous for Boeing to ask for it, given that the FAA already approved the same thing previously.