My experience:
(1) True, but that is why we have scalpels (or X-Acto knives, etc). Typically, when encountering an instrument that had finish applied after the neck was glued (or bolted) on most NRSs (Neck Removal Specialists - I just made that up) will warm the blade and score the heel and fingerboard extension, cutting through the finish, prior to attempting to remove the neck.
(2) True, but it is in there, we just know it. ;~}
(3) True. How many there are out there? I certainly don't know. I encountered another "excessive glue" Guild during this 12 string rebuild (see 1999 Guild JF65-12 Overhaul).
(4) True, with reservations. Subject to damage? Yes, including crushing, warping, etc. especially in the hands of someone who is not as knowledgeable or careful as they could be. Guild neck heels vary/varied in thickness, and the amount of energy needed or used to remove the neck had/has an impact on outcome.
(5) When (inevitably) compared to a Martin, a Guild neck heel is much wider, providing greater surface area for additional glue (in addition to glueing the fingerboard extension to the soundboard and glueing the dovetail joint, the heel is glued to the sides. The larger the heel, the greater potential for more glue to be applied).