4 cm are not only not harmless but even more than worrying!
I see this ambivalently: on the one hand, the statement that this is statically harmless is not entirely wrong. The house will not collapse just because construction continues on it. but: this obviously does not apply with the same static calculation, which would have to be redone!
And that is considerably more expensive than tearing down the wall and rebuilding it.
OK, it seems that we are facing a bigger problem then. The filigree ceiling has already been installed and concreted.
Oh dear, how is the respective wall positioned in relation to the direction of tension of the ceiling? ... however, I still see more than just a slight chance that it will not have to be demolished.
We then have to seek the conversation tomorrow.
I see the urgent necessity to send a formal written complaint about defects immediately and verifiably. How the demands contained therein should be formulated, I would definitely not draft without a lawyer. And indeed, one specialized in construction defects, not in marriage contracts.
What is supposed to come out of a "conversation": Until then, you will have remained a layman and accordingly will not be able to assess what the fool is telling you.