You are right, and what you say makes perfect sense, but this is how it goes....
Prospective purchaser/owner having probably just gone through an exhausting period sourcing the desired aircraft, then survey, pre-buy etc etc is then tasked with getting the aircraft home. The first thing is obtaining ferry quotes, working on the assumption that all companies/pilots are legally able to perform the duty/service that they are advertising. This process can be just as exhausting as the purchase itself. The Email exchanges with various ferry companies presenting different alternatives/routes/equipment/costs etc etc is then taken on board for comparisons.
I think I can speak for everyone here [definitely myself] and this is when the *due diligence* process then registers to the next stage of checking this type of finer detail, however, the modus operandi of weaver is to conclude the final part of his sale by telephone. He will call and adjust the cost down significantly stating that he has a cancellation, and if you wire the money to his bank account immediately a deal is concluded. He is very very convincing.
Of course, all details are confirmed by email as the money is wired to his bank account. After that process the fun really begins.
That said, at the time of my ferry, the medical/license scenario would not have helped much as he was current, albeit with a fictitious address.