As far as we know there may have been a strategic discussion involving these gentlemen any by the time "we" get to the briefing room they contributed what they had or could contribute:
KIRK: The design of the ship is the same. Mister Spock, you said you had a theory on why your sensors didn't pick up the new ships until they were upon us.
SPOCK: I believe the Romulans have developed a cloaking device which renders our tracking sensors useless.
KIRK: If so, Romulans could attack in Federation territory before we knew they were there, before a vessel or planet could get even begin to get their defences up.
(Notice the show Kirk and Spock put up in front of the others, already well aware that the Romulans did
develop a new cloaking device
That's an interesting theory but wouldn't McCoy and Scotty have gotten suspicious about their presence?