Disturbing SPELLS_CHANGED behavior

[BDelacroix]

Yes, another question.

I am reading this about the SPELLS_CHANGED event and find it disturbing (in bold).

arg1 nil when the char learns stuff. Also when changing weapons and shapeshifting. In addition it seems to be called on regular intervals for no apparent reason.

Is this indeed the case? It would be nice to have a way to detect only in cases where the player learns a new spell. No biggie, I've worked around it as well.