Correct....
I can't remember exactly, but the limitation applies to takeoff....where the local airport is not WGS84 standard and the difference is not negligible, the GPS must be deselected.....and cannot be re-selected until after takeoff and a safe altitude is reached. (However that's defined....)
The issue, in my mind at least, is what defines 'negligible'. Unless your airline specifically states the difference is definitely negligible, then I'd say you are mandated to follow the limitation.
What airports are not WGS84? Don't know of any personally.....
Fly safe,
PantLoad