You have to wonder why the lettering "G/S INHB" was even included in the switch design.
If the G/S INHB legend doesn't light up during general GND PROX warnings, when would it illuminate? The switch is black when there are no warnings (so the legends are not visible).
Note that Korry switches only have 4 bulbs: Two (side by side) for the upper switch half, two (side by side) for the lower half. There is no individual control for single lamps in a pair, which means that if the G/S INHB illuminates during a light test, it has to illuminate during a ground proximity warning.
I doubt very much that GND only illuminates during ground proximity warnings (that would be nonsensical). Both GND and PROX must illuminate.
The only way the switch manufacturers could stop only the G/S INHB legend illuminating is by putting some kind of obstruction between the lower lamp pair and the G/S INHB legend. If they did that, the "G/S INHB" legend would never be seen (including during lamp tests).
If the switch is pushed below 1000', but prior to a glideslope warning, is there any visual confirmation that the inhibit mode has become active?