Agree it is a stupid policy. As long as there is no fire, at least let people grab their carry-ons.
edit for clarity: I understand the issue you face regarding your medication being trapped on the plane and believe airlines should indeed have a duty of care to ensure you have rapid access to replacement medication at their expense, but I'm specifically addressing why they have the policy of telling people to not grab carry-on items during evacuation.
If there is actually an imminent threat to life, such as a fire, of course all of these things should be left behind. But I'm of the opinion that in no event should anyone's health be compromised in the name of a blanket policy to collect "evidence".
In short:
save lives >> protect health >> collect evidence
Especially when those policies will obviously piss off a bunch of people, I can either assume those people who spend decades thinking about X don’t know what they’re doing, or I can say “hey, I probably know way less than they do.” That doesn’t mean I don’t inquire/don’t question, but I think jumping from an unattributed off-hand remark in a CBS article to “FAA is dumb and they’d have let me die on the tarmac” deserves some skepticism too.
I am genuinely curious about what exactly this policy is, why it exists, and how they handle cases like yours. I don’t think “assume the people who investigate aviation incidents aren’t aware there might be medicine onboard” is a good starting point for that type of inquiry.