PS5 will not have the same problem because even if Series X is 560 GB/Second , some RAM modul run slower at 330 GB/S. while PS5 has unified number speed with 448 GB/S across the memory setup and has the same 16GB amount of RAM the same with Series X.
Not true. That's one of the points Cerny missed to address. The XSX can use 10Gbytes of ram at 560 GB/s. That is the obvious place where textures, frame buffers and all the key stuff is allocated. The compiler/linker will make sure of that, all games, all the time. The PS4 only has 448GB/s. If 448 GB/s is enough for safe 4k/60Hz I'm really not sure. The games wil tell, but I think this is a gamble (simply for using lower priced ram chips) that might not pay off in the end. On the same games, the XSX will have more (native) pixels on screen. On the other hand, the PS5 will have the "better" pixels if all the ssd-tricks are used.