I don't think you understood what I meant. With consoles like the PSVita, the PS3/PS4, Xbox360/XboxOne, there are no ''ram stick'', the memory modules are stuck to the motherboard and you can't replace/upgrade them. It's not like a regular PC, where you have a slot on the motherboard that can accommodate different RAM configurations, depending on your needs.
Of course you can run more apps on 16GB of ram on a PC than if you had 4GB, because the software on the computer will allow more apps to be opened when more RAM is available, up to a certain limit. The same is not true for a console. Their software is optimized to only use what is available to the console, so it wouldn't allocate more than what it comes with, even if the memory was available.