I'll just say that separating CPU and GPU in console gives it same disadvantage PCs have. That's need for separate memory controllers. And that leads to need for higher than minimum amount of memories installed = increased price. If PS5 had 3x 4GB HBM2, it would have plenty of memory and plenty of bandwidth. In separate scenario, CPU will have 2x DDR? (likely 8GB) + some adequate graphical memory technology (likely another 8GB). Another issue is that regular RAM eats quite more from power delivery/consumption/cooling budget.