Yes but those instructions came too late to stop the aircraft coming within 7NM of each other at the same level, on a collision course. That, by definition, is a "failure of separation". "Late ATC intervention" is a "failure of separation", involving much form filling, suspension of the individuals involved, official reports, etc. I'm coming to think your definition of "separation" is "not actually hitting each other", which is not an industry standard!
Following your argument through would mean that if ATC fails to separate traffic before it comes inside the 7nm limit, the controller should shut up, and leave it to TCAS to do the job (or not). Better to take the risks of TCAS failure, than to violate an industry standard!
I don't think you're advertising that course of action.
But what, then, is your point?
Bernd