“but I wonder about things like the suit’s ability to protect them in an emergency from thermal or pressure changes if its fit is only a rough approximation.”
Space is dangerous even if everything goes perfectly.
Boeing has proved they have no business operating in that kind of zero defect environment.
Just a clarification: I should have been clearer that I was talking about the fact that the crewmembers’ Starliner spacesuits would not be compatible with Dragon, so SpaceX would have to do their best to send up SpaceX suits that would approximate their body dimensions as closely as possible. I also wonder how quickly that could be done since spacesuits are essentially handmade, and I doubt SpaceX keeps spares just lying around. I wonder how long it would take to produce them?