If you start on the 7th fret of the A string, move BACK 5 frets, and then down to the D string
or
Start on the 7th fret of the A string, move UP 5 frets and then up to the E string
you will land on the same note. 7th fret, A string is the note E. Moving back 5 down 1 will also land you on E.
So start on the note C (for the C scale) on the 3rd fret of the A string. Move up 5 frets (now on the 8th fret) then jump up to the E string. This note is also C.
Don't really understand what you mean by:
"as a way of making the distance between notes on the scale shorter"
Edit: Another interesting way to look at this is by starting on a 5th fret. I'm assuming by now you know how to tune the guitar by tuning the 5th fret of one string to the open string below it. The reason this works is because of that concept you are talking about.
Start on the 5th fret of the low E string. You can go down 4 frets to fret 1. Going down one more would require you to play the string open. Then move down to the A string (5 frets down, 1 string down) and you are now playing the open A string. Both pitches are the same.
You are basically starting on one note and the finding the exact same note somewhere else through this helpful pattern. I can't watch the videos but I am ASSUMING that this is basically what he is doing. Finding 1 note somewhere else in order to maybe find an easier way to play a scale.