I agree with that. There's so many factors that go into how often you can lift such as intensity, volume, experience level, etc. Assuming you kill it in the gym like you said in an earlier post, I agree that the 3 day rest period is a good rule of thumb. Although that's really all it should be looked at as and not set in stone. If you're feeling amazing after only 48 hours, there's really no reason you couldn't go in the gym and hit a new pr. Routines like 5x5 use sub-maximal loads where you aren't killing it every workout and the body can recovery more quickly because it's an easier workout...just done more often. Neither way is wrong, just different ways of getting to the same goal.