I can't afford to have them made and assembled to find out that there are critical errors.
Always test the PCB with a small sample before going to low volume production. Don't bother getting PCBA done for a sample
Just get a panel or a few PCBs made using your final gerbers and then hand assemble them according to your final BOM.
Test and confirm everything is ok.
Skipping this step is something people do do, but only when they have many PCBs under their belt and have put it significant time checking over the PCB. Usually by more than 1 person. And even then, problems still slip through from time to time.
However, if you are contracting the development that maybe something they should do. I dunno, depends on your agreement with them