<<<<<"Not having any discussions with the FDA after the positive advisory panel vote strikes me as odd (no labeling discussions, no post-approval 9902B discussions?)">>>>
You can find FDA written guidance that states there is to be no clue or hint given to a sponsor as to the final decision until the letter is issued. The draft label is submitted a long time ago, and the FDA can mark up revisions in pencil, and send it to the sponsor conditionally and any-time.
I have not read it in a while, but I believe the reason given is that the decision may change as it goes up the line, or upon further review. The FDA does not reveal differences of opinions between staff, only "consensus" documents. Obviously they don't want a marginal decision to be seen to be a case on one individual over-ruling the staff. Cannot argue with that.
"....on the biotech battle-field, you need some élan...."