you failed to notice that the engine had a giant air leak? - it would also have a lean stumble.
The engine coming up to temperature - has nothing to do with the PCV, I can list you a lot of things caused by bad PCV.
oil being pooled into inlet manifold and burning,
balking
lean stumbling
knocking
bogging
oil turning to tar
anyways - theres a lot of things that can lead a mechanic down a wrong path, e.g. I have a business here that solves driveability problems on passenger cars and trucks and operational issues on heavy equipment too. I can sort of see both ends of the situation.
you think you were robbed
the vendor thinks he was robbed.
you had no between solution - hence for you that person is bad, and thats OK too.
the reason I say this - you mentioned idling smoothing after IAT disconnect and then mention PCV - which on wording makes it cancel out. - but all is good and believable.
OTOH, we never got to know the wordings of the person working on it. - I have got dozens (infact hundreds) of such experiences