I think you'll find that some SS will allow and some wouldn't. I got lucky with our one as he didn't mind as long as we provided the materials on the day that the tradies were doing it. they don't delay it for you. that's how I got the noggins / doors / cabling done.
I have an issue right now . Last week i was told all plans are finalized and we will start construction soon. Then yesterday they are telling me that the floor tiles that we have selected is not same as glendale and the grout that is available with them is ' silver grey ' . Whereas the one that suits is ' antique white ' . Do you think i can ask the site supervisor that i will supply my own grout at the time of tile layout.