Looking at the situation, I would guess it's exactly that - long-term guarantees against being cut. He only has two years left on his current deal. He is already $2+ mil/year ahead of the current highest-paid OC in football. Next year, his base salary spikes (so not guaranteed), and his cap hit would be 24.4 mil, but they could cut him with a dead cap of only 4.4 mil.

Keeping him beyond '25, from GB's perspective, would likely mean a salary bump, which would mean keeping him as the highest-paid OC in football (and probably increasing the distance between him and #2).

Therein lies the issue. Moving to OC means moving to a lower pay scale position... his contract is one of the highest paid players at a higher pay scale position... he is disinterested in losing any future earnings... and there you go.