Ann: Remestemcel-L FDA Fast Track Designation for COVID-19 ARDS, page-365

This seems logical, but can you humor me by having a look at my questions below?

If this was a legal requirement, why did it take the FDA until pretty much the end of the process to inform Mesoblast via a CRL?
They had plenty of chances:

1. Rolling review - could they have mentioned this legal requirement?
2. BLA - could they not have rejected the application outright? It's either a mandatory requirement or not!
3. ODAC - why bother with this process, if the legal requirement has not been met?
4. ...

Now, I don't fully know the technicality of the trial and the trial design, but based on the above - something does not add up to me.
If this is a mandatory legal requirement and the FDA have identified this; then why didn't they perform their regulatory duties and inform Mesoblast earlier?

Maybe, just maybe trial was considered “adequate and well -controlled” by the FDA - until, they've flipped late in the process and then deemed it wasn't!