It is impossible for us to tell from the video whether that was a good hit or not. One possibility was that the cue ball just barely feathered the five ball, hitting it just enough that it would wiggle back and forth in position and not move more than 1/10 millimeter, and then the cue ball hit the four and then the cue ball hit the five again (backwards). That's possible.
Agreed. I considered this possibility, too, but thought this type of contact would likely be "imperceptible" to a typical referee and a foul would not be called.