strange Air filter location

My AC has a really bad smell coming out which i thought might possibly have been a mouse that died after building a nest in the air filter (happened to my brothers taco so i figured it might be the case) but it turns out it's just mildew from a little water that got inside the air ducts. so my question is not how to fix it. what i really want to know is why the air filter is located behind the radio assembly rather than behind the glove box? there is a small air duct that pops out behind the glove box where the filter should be. when i look inside i can see the filter set up directly behind the radio assembly. i don't think it needs to be replaced but i wanna know why its set up there and not behind the glove box? anyone heard of this design?