Can still see track in ceiling a remaining wall of walls removed?

It depends what he has written in the schedule of works , if he has agreed to make good all repairs which have occured from the works undertaken or defects from moving or removing old items , then yes it should be filled/ plastered and then painted to match the surrounding area. Myself as a painter/decorator if I'm aware of the defect , I certainly wouldn't/couldn't leave it in that condition , it would bug me.

If you employed a builder that organised the whole job and your very happy with everything he’s done apart from a few marks in the plaster then I think he’s done extremely well.. maybe a bit harsh if you criticise him or complain... just have a nice chat with him and I’m sure he will rectify it... You mentioned you have paid him a lot of money... but in return he has done a lot of work for you, so you’ve not give it to him for nothing and Mentioning giving him money shouldn’t even come into the equation

First of all you should have uploaded a picture of the track line you can see in the new plaster. From what you have written It sounds like an old door has been taken out and moved back to allow for a new stair case to be fitted. Assuming the old door frame was screwed to aN existence brick wall ur man should have chased back the brick work, apply PVA glue over the raw brick wall, Then apply one coat of Hardwall then pasted over the entire area twice. He shouldn’t have cut any corners and you (Assuming u did) shouldn’t have gone with the cheapest quote. It’s just how the cookie crumbles sometimes.