I disagree. I’d say 1 out of 1 pilots do not fill out the medical express forms truthfully. Every single one that ever played on a merry go round as a kid and answers no to ”have you ever been dizzy” is not being truthful, just as a minor example. The form doesn’t differentiate between causes.You said “very few people lie.” I’d say over 1 out of 2 pilots not being truthful in a sample set of almost 4,000 pilots isn’t “very few."
Further, not one of us actually knows every diagnosis we’ve ever had as we do not have memories or access to records that go back to birth. We’ve all “lied” on the form in that respect. We do the best we can, but nobody can actually say they know for sure.