WHBM
The FIDS themselves are confusing because they show the gate numbers, but there are no gate numbers displayed in the "new" upstairs departure lounge, there are door letters A, B, C etc instead which lead to stairs down to the actual gates, each signed for a certain flight, although it doesn't seem to matter which door you go through at all ! Whoever thought this one up ?
Seem to recall that the fids list both the door number and gate. You're correct it really doesnt matter which door you use but if they weren't defined then 3 airlines could all try to board flights at the same time through the same door - potentially over 400 pax.
So who thought it up - probably the same person who thought it through.