that is... wait for it... DISCRIMINATION! And I add a bit of volume there.
The staff asks: Really?
Me: Of course!
The staff: Sigh... sure, we can add another taco, no problem.
8 minutes later...
Taco plate arrives without taco replacement.
I point it out...
The staff: ohhh... sorry for the mistake. Let's see what we can do.
8 minutes later...
Taco plate arrives.
I just wonder... what if they would just have given me the option to replace the taco from the start?
If they really believe you are allergic then they might be afraid you get an allergic reaction if they simply take the old tacos and remove the mushrooms because a trace might be left over or they might miss one mushroom
Naturally no tip was paid.