The FDA threw the potency assays thing at MSB because they are...

The FDA threw the potency assays thing at MSB because they are in "unchartered waters". Not that they haven't been closely involved in every stage. In fact MSB has been integral to developing protocols to eliminate shonky operators and guided the FDA through that process via Silviu Itescu and staff.

However. Each new official often present dangers. They can want to reinvent things. If they're so stupid as to ignore their own expert Committee with 9-1 majority, the emphasis being on EXPERT you're going to get numpty criterion like potency assays. I'm not going into the issue of conflict of interest with the 1 dissenter and the influence he may have had. It's been dealt with elsewhere.

The main issue is that because this is a therapy involving human cells, the FDA which historically has been geared around controls of pharmaceuticals in this space, is trying to make themselves appear in control.

The fact is they don't understand the mechanisms by which this works, BUT that's never been a precondition for pharmaceutical drug approvals! Plenty have been approved without this complete understanding.

So why bring on this? You get a bureaucrat afraid to stick their neck out and/or wanting to make a name for themselves as appearing in control? Perhaps all of them plus the conflict of interest issues that have been lurking.

The reality is that MSB could litigate against this stupidity, but they're still trying to keep the FDA onside.

Now they will politely demonstrate the inappropriateness, of this criterion. As I have said before, MSB has said at the outset in the webinar after the referral letter last year, they are confident about the legal precedents involved.

These are my reasonable guesses based on this context.
This part of the Ann is entirely consistent with my prior guesses so far. MSB is just having to be polite about it.
I would have liked to be a fly on the MSB wall when the FDA decision came out last year. My strong guess is a few expletives were issued.
As in What The ???? SI's blood pressure was certainly raised. For such an intelligent man, indeed for the intelligence of the entire team, it's absolutely confounding.

My guesses are also connected with having worked in bureaucracies and seen this kind of thing before, many times.