You've never been able to upgrade RAM on GPUs for the exact same reasons that Framework is alluding to. That's what's happening here; GPUs have lots of cores, and to keep them feed you need lots of bandwidth to go along with it. All dedicated GPUs come with dedicated memory for this exact reason. Things like traditional "iGPUs" that use DDR can get away with it exactly because they are so small and computationally weak that the limited bandwidth isn't the immediate #1 bottleneck. But Strix Halo is not intended to be a measly iGPU system, so it has different needs.

There just isn't a free lunch here, it's an inherent design tradeoff for these kinds of chips. The CPU is just along for the ride, in this case.