This is the correct behaviour as you are trying to add entity event handler to projectile https://community.bistudio.com/wiki/Arma_3:_Event_Handlers#Projectile_Event_Handlers

But i'm not trying adding the "local" event to the object myself, i'm just calling BIS_fnc_objectVar, and inside Arma3 code (/temp/bin/A3/Functions_F/Objects/fn_objectVar.sqf..., line 53) its attempted to add the event.

P.S. Confirmed by checking BIS_fnc_objectVar in Eden Function Viewer.

OK, let me explain. "local" even is for objects classed as "entity", you are passing the object classed as "shot", which is what projectiles and mines are. Shots don't have "local" EH hence you get no EH error. This is not a bug.

BIS_fnc_objectVar is suppossed to give me back a string name for a object. That it requires a "entity" object and does not support "projectile" objects is not obvious, especially as that kind of differentiation doesn't seem to exist in sqf, at least to my knowledge.

Is there even a way in sqf to detect if a object is a "projectile" or a "entity"?

Shouldn't BIS_fnc_objectVar at least itself detect if the object is a proper one and only add the "local" event if the passed object is of the proper kind?

That it requires a "entity" object and does not support "projectile" objects is not obvious

BIS_fnc_objectVar is a script function, scripts do not know what type of object it is just that it is an object. I am telling you the cause of the error, now you know too so you can avoid passing unsupported objects