so let me see if i understood it correctly :
if i delete lets say far cry 3 on a PS4 it will be deleted BUT if i log in on my PS3 the game will still show up there??
thats kinda weird and stupid to be honest...
That's correct.
They may be able to update the PS3 so they don't show too, though the last few PS3 OS updates have been very lacklustre.