It clearly does exist as a concept to the PLA if the Taiwan MoN reports are too be believed. PLAAF regularly flies just across the edge and back. They almost never intrude any further.
Yes, that's the trick. You'll be putting you faith into an agency that was first saying no missiles overflew Taiwan, then when was called out by Japanese MOD saying not only did DF-15 overflew, it actually overflew almost directly over Taipei they came back with "but but the missiles were more than 100km up, therefore in space and not in our airspace".
There's already so many cases those MND report being proven false. Not the least of which is the fact that they show PLAAF aircrafts taking physics defying hair pin turns.
To tie this back to the thread. I recall last year in particular ROCMND reported once an unusual number of J-16 in the strait, to the point that if it was real you could build a whole J-16 wall flying towards Taiwan with minimum space separating them for safe operation and still not reach the number quoted. I recall we were suspecting that this was an artefact of them falling for J-16D or other means of EW.