No, that is not correct. If you have any idle processes, their memory can safely swapped out without impacting performance. The user should not be forced to quit programs as soon as they become idle. Also, as described in the article, a program often allocates pages, which also become unused and can be swapped out. In an ideal world, a program would not allocate pages which become idle, but that happens with complex software (and often depends on the user interaction, and thus is not completely predictable). Swapping out idle pages is a very simple solution to make more memory available for the active processes.