They're not.
I encourage the GSE's to get home inspections on all of these properties.
Let's call it what it is - guess the age. You can't guess an age of the roof. I've seen 2 year old roofs under trees that look like it needs replaced. And I've seen 20 year old roofs in the open that look brand new.
I suspect like most other things in this profession, the folks that make this **** up are on the take. Maybe roof companies have offered them money to get lists of homes that might need a new roof.
I put nothing past these folks.
I'll be putting N/A on most of these fields. That's what you can do when you're independent.