It is not part of L1 and L2 (as those are just the levels Ive taken)...
Though a short discourse on it is found at the TOTW2 DVD... Pretty much - rev matching with the clutch is not recommended. If you have to do it, do it in the lower range, ie., maybe not more than 2,000.
However, in race/track sessions, it is a valuable tool to have in your cabinet of tricks. Say, you are coming in to a corner in high-revs, and you made a wrong shift (your blip was either too strong or too weak, etc.), learning to modulate through the clutch (sometimes open/closing a few mms around the "meet poinyt") is your only recourse to avoid a mishap.
Could anyone else chime in on this?
On the other hand, knowing how to do brake/blip/shift is nice when you come into the lessons/Levels. There are corners that, when allowed by your coaches to go "full brakes and full gears," FUN to take in...