Another libero replacement question.

[Scrapper1]

Let's say the libero is in the 5 position, and there is a rotation, and the libero's spot to serve is next. The libero is not required to come out of the lineup, but is allowed to immediately replace the player in the 1 spot. I don't have my book in front of me, but I'm pretty sure I'm right about that.

When this happens, there's a weird replacement/substitution sequence that occurs. One player enters the court from the bench, and one of the non-libero players leaves the court. This is not done as a regular substitution, when I've seen it. Everybody just says, "It's for the libero" and the players make the exchange without using the substitution area.

Is there technically a substitution taking place? Should a sub be recorded on the scoresheet? What is actually happening when this occurs? L (would be the new 4-spot) replaces the new 1-spot. A player comes on to fill the 4-spot. How is it tracked on the libero tracking sheet?

I'm sure it's legal, because everybody does it and no ref ever objects. I just don't understand it when I see it.