Who is your builder?
Ask them who does the 'low-voltage' work.
As I said, I am building a home - non-custom for sure! It's just a pre-fab, built in Pennsylvania jigsaw puzzle that is shipped to Virginia and assembled. Not custom at all.
But, the wiring is still done by regular guys who run wires and in THIS day and age, having CAT-5 (ethernet) run anywhere you want it, is just allowed. It was like 60 bucks or so for any single ethernet or cable outlet that I wanted, and I picked where it went.
They also had 'audio wiring' packages. I told them I didn't want their speakers, I didn't even trust their quality of wire. Almost immediately I was working directly with the person who was actually going to be pulling the wire. I ended up being out there the day they pulled the wire and I made SURE every wire not only was pulled, but that it was where I wanted it and was correct.
I believe that the guy pulling the wire was really excited about doing something a little different than normal, and it only took about 14 hours to do the wiring. This is something you PAY for, so if they won't do it themselves demand the right to have an experienced professional do the work, or find another way. Go in at night - whatever. I am 100% behind the belief that this is YOUR home - you are paying for it - and they should be doing it your way.
In my opinion, home builders are complete morons. Not the actual laborers, but the management offices are totally inept and out of tune with client's needs and expectations.