I have not done the TAT, but I did the Continental Divide in 2015. GPS Kevin's route for that trail had errors, including going through closed lands.
If the "other guy" is Sam, he is the guy that originated the TAT trail. I would not be opposed to compensating him for his effort and knowledge. It is worth it to not get lost or confused while on a trip.
Whatever you do, you should view your intended route in detail in google earth to validate it. I reviewed a couple CD routes and was surprised how sloppy they were. For that trip I created my own file, but that was a lot of work.