I think it's great to have standards, and expect them to be kept.
Most of my customers expect really high standard work. So I wouldn't do as he's done and put the elbows like that. But it all comes down to time.
The old adage "time is money" is never more true than in plumbing.
Our time is a finite resource, and if you want a plumber to lift the floor to hide the pipe work, then he will want more money to do so.
If you were all agreed on this, and he blatantly ignored you, then you have every right to give him two options.
1. Come back and finish the job as you agreed.
2. Let someone else come and do it, and you with hold the money it costs you. (there is no reason you should have to pay twice).
Good luck!