Machinists are human. We make mistakes.
If you want to assemble engines you better damn well know how to correctly measure things to verify it is what it should be.
For example, let’s say I have a crank and I want .0023 clearance. But I check it myself and I get .0039!
Do you let it go even though that’s almost DOUBLE the clearance you thought you wanted? Thats HUGE.
Or do I stop and start going through the process of validating the tools and methods used?
One way or the other the end builder is responsible for knowing what’s going together and how.
You measure EVERYTHING.