But it is. Of course the astronaut can’t check let’s say every possible screws are properly tightened, but no single human can. So what can an astronaut do who is concerned about screws comming loose do? They go to the engineers who designed the craft and ask them. The engineers show them the various calculations and work documents showing how they sized the screws and how they calculated the appropriate torque they should be tightened to and why they think they won’t come loose. The engineers would also tell the astronauts that they specified twist wire as an additional safety mechanism on top of all of that.

And then the astronaut can head to the head mechanic who leads the assembly process and ask them how do they know that the screws are torqued right. They would show them the training the technicians receive, the tools they employ and the QA processes they have in place.

After that the astronaut can spot check a few areas.

Of course they won’t do all of this with all of the systems and processes, but they can do enough to satisfy themselves that the place has the right processes in place to their liking.

If the engineers don’t care about the screws, if the chief of technicians can’t find the calibration paper of the torque wrenches and if they find a passed out drunk technician behind a panel and rattling screws then the astronaut knows they are in trouble.