Agreed, this doesn't make a whole lot of sense for PS5 based on the conventional alternatives, which are known quantities.
The patent is broad enough to cover a lot of bases in terms of the material or how it's applied.
In terms of how AMD GPUs and Sony's consoles have had spotty results in terms of mounting pressure and grease application, an interface material that could give good enough performance even if their application skills do not improve might be tempting.
One scenario is a metal compound solid at room temperature that melts during operation, which might allow applying the material as a pad like the phase change pads on some coolers, or like the graphite thermal pad used on the Radeon VII.
It would combine a more readily positioned and applied layer with at least some of the performance benefits of the metal.
Unfortunately, the references I've seen for this sort of application seem to have come from the manufacturers of such materials, and I didn't see reference to an application with the chip size and production rate like a console APU.
Given the extra effort, is a fancy TIM a better solution than improving some uninspired cooler assembly processes? If there are other reasons that are more pressing, like hot spots or thermal density, it might be considered an neat expenditure of creative engineering for a design corner that seems like a mistake to find oneself in.
Gallium would be an example of a pure element that would have the desired melting point, although chemical and cost considerations intrude. It'd be interesting to see what sort of warranty sticker Sony would need to absolve itself of responsibility with a TIM that could potentially disintegrate parts of the tools or setup of a user trying to service their console.
