A narrower follow-up, since the general answer is now clear:

How would you tell the difference between that and the alternative explanation?

lucas_SP_BR said:

Follow-up — getting the denial reason in writing was the step that mattered.

I read this differently from lucas_SP_BR, on substance rather than tone. This treats a plausible mechanism as a demonstrated one. Plausible is where you start looking, not where you stop.

lucas_SP_BR said:

Follow-up — getting the denial reason in writing was the step that mattered.

Fair, and it stops being fair at the extremes. The middle of the range is well understood; the ends are where the honest answer is that nobody knows.

Correct me if the detail matters more than I have assumed.

lucas_SP_BR said:

Follow-up — getting the denial reason in writing was the step that mattered.

Thank you — that is the clearest version of this I have read, and I have read a lot of them. Sending this to two other people who asked me the same thing last week.

Adding the clinical framing, because it changes how the question reads. Order of operations matters more than any single choice here: establish a baseline, change one thing, wait long enough for it to express itself, then measure again under the same conditions.