2 Man - Ball-Side Mechanic

[BLS]

First post to this site from a rookie!

I'm in my first year of reffing, so have been studying the Rules Books, Casebook, Mechanics, etc., and have a lot of learning to do. My first of probably many questions:

Worked my first game last night (MS girls).... As part of pregame, I asked my partner about when Lead should shift to the same side of the court as Trail. Partner (8 year veteran) looked at me funny and said "never - Lead should always stay opposite of trail in two man" So I felt kind of stupid and said O.K.

After the game, I checked the Officials Manual and sure enough found the section that discusses Ball-Side mechanics for Two-Man (2.3.3 of manual).

Here's my question: Does anyone use this mechanic in two man? If so, do you rarely slide over (i.e. only if all ten players are on your opposite side.) Is this mechanic relatively new?