Let's forget what we've already invested in this idea; a simple Google Forms survey does not suffice to explain the complex behavior of document verification.
This type of survey describes what happens but does not reveal the deep motivations behind why 75% of travelers verify their papers so early.
In Switzerland, for example, our culture of punctuality and respect for administrative rules naturally push us to anticipate these procedures, regardless of any observation.
We do it out of habit and to avoid unexpected costs or delays, like missing a flight due to an expired passport.
The survey observes, it does not cause the behavior; we should see a correlation, not a causality.