as long as you know that the other aircraft are in communication
That's true, but one can NEVER know for sure. Radios can and do go bust, though rarely. There are NORDO planes around, even if they shouldn't, in controlled airspace. (I remember a story about a Swiss BA146 on long final for EBBR 01 at FL080, suddenly observing a trike to their near port side... only a barside story, of course... ) More commonly, pilots will tune their radio incorrectly - ever set 129.60 instead of 126.90? I have! - and fly on merrily, blissfully unaware of their NORDO status.
I feel I begin to sound like a broken vinyl record, but never and nowhere should we blindly trust radio comm's, or the lack of them.
[[ regarding mutual familiarity tower operators vs. pilots: some strong stories around at EBAW Antwerp, particularly regarding one RdV
Largely confirming your position ]]