Closely guarded while on the move?

[Amesman]

Realize the definition and stipulations for "closely guarded" calls but looking for some clarity on something.

I "get" that closely guarded is commonly called for guard play that lingers near the division line or simply moves laterally. But seeing these two observations in another forum today reminds me of a question from an earlier posting here:
• Once the offensive player gets head/shoulders past the defensive player, the count shall stop.
• If the defensive player backs away (more than six feet) the count shall stop.

It almost sounds like this call can be whistled if a player is closely guarded but never gets his head and shoulders past a defensive player on a slow (OK, very, very slow) dribble to the basket, or, say, if he/she backs the opponent down toward the basket for 5 seconds.

What's the rationale for not calling this? Can't remember seeing this called this way. Nothing popped out from the books just now, though it is pre-coffee time, so apologies if it's waiting right there, ready to knock me on the head.