Instead I feel it's the opposite because that memory is shared with the GPU. So if you're gaming even with some old game, it's like having 4gb for the system and 4gb to the GPU. They might claim that their scheduler is magic and can predict memory usage with perfect accuracy but still, it would be like 6+2 GB. If a game has heavy textures they will steal memory from the system. Maybe you want to have a browser for watching a tutorial on YouTube during gaming, or a chat. That's another 1-2 gb stolen from the CPU and GPU.
Their pricing for the ram is ridiculous, they're charging $300 for just 8gb of additional memory! We're not in the 2010s anymore!