> Or maybe, “No Ukrainian or Russian aircraft - NATO aircraft will shoot down both.”
Not really. Response to any Russian aircraft shot down would be sending a bunch of rockets to the place from where the aircraft was shot down; whether the destination is NATO or not.
From there, it would escalate quickly. That's why NATO generals and saner politicians are not enthusiastic about it.
TL;DR: trying to enforce no-fly zone would hurt. Too much to be worth it.
Its not a misnomer at all - it is exactly what it says it is - might not be a good idea, but calling it a 'no-fly zone' is completely accurate.