Charging rules

[Liebchen]

The defending units must not consist entirely of Infantry in Square formation with Leaders and/or Cavalry. However, if only Skirmishers, Artillery, and Supply Wagons occupy the defending hex with Infantry in Square, then the charge is negated.

This is a confusing sentence. Why not simply say that there is no charging melee bonus when attacking a hex with an infantry unit in a square, even if there is also a Leader, a Cavalry unit, Skirmishers, Artillery, or Supply Wagons in the hex. Or does it mean something else?

Is it also saying that there is no charging melee bonus when attacking a hex with a Cavalry unit in it? If so, is this linked to the presence of the infantry in a square?