I asked myself this very same question, and I came up with reasons why it might work in both ways.
On one hand, getting rid of the spell should reveal everyone.
On the other hand, getting rid of the illusion on the caster wouldn't necessarily, as the magic still lingers around the other people.
Anyway, it's neither intentional or a mistake (yes, as odd as that sounds). It is what it is, at least for now, until I a) decide and b) dredge up some time to change it, if in fact it is to be changed.
