I think a lot of this has to do with the astronaut being the practical
voice. How many times have you heard the phrase "engineers don't use
what they design."

I hate to do another FTETTM reference, but in "1968" there's a great
scene where Borman is in the design room at Downey talking about
redesigning the hatch. The new hatch is put on and Borman sees what
they're doing and says "wait a minute ..." He then grabs a chair and
sits in the CM skeleton like he's seated and then shows the engineers
why their design isn't going to work PRACTICALLY.

I think this is the kind of input the astronauts gave. They saw where
the engineers were going and then said "okay, let's look at this from
the astronaut's" perspective ...