Something just occured to me: During the mindmeld something iconic was missing...Spock didn´t say the "My mind to your mind...etc." Was this ever adressed in an interview? Or is there any precedence during TOS for Spock NOT saying it?
The meld with the Horta comes to mind. The attempted meld with Landru-programmed McCoy is another. Several other instances of non-verbal melds may be found in the list here
I think one thing to consider is that, in the case of the meld seen in this movie, the other party was unconscious due to being hit with a phaser set on stun. Would there have been any point in speaking the words to a stunned Romulan who would presumably not be capable of comprehending them?