That is an interesting assumption that the gear is automatically not GUE philosophy compliant.
When I took Fundamentals, the only things that I had to change were the length of my hoses and my console computer, (a Wisdom which was starting to give odd readings) to a wrist one.
One GUE instructor outright just gave me a pair of jetfins that were gifted to him by an LDS - 1.5 years before I ever even thought about taking the course.
GUE divers lent me long-hosed regs to try and had pool sessions with me to practice S-drills.
The GUE instructor intern lent me one of his bottom timers for months before the course until my chosen computer became available.
In GUE fashion, I have also lent out gear many times to divers as well as mentored them. The instructors tend to travel with a trailer full of entire sets of gear and I've seen them just lend them out. These days, in certain areas like the Great Lakes and rivers, many divers have philosophy compliant gear more often than not, even if they're not GUE. Either way, it gets borrowed or rented quite often.