I have ran 11” rotors on my dirt cars both front and rear that utalize G body brake calipers for years. Even on stock front spindles. The pads actually sit really good on the rotors and the bracket is made for an 11” rotor. I see what you are saying though, if they made a bracket and rotor at the stock 10.5” size, it would definatly give me the clearance.
Exactly. You can have that thicker caliper body when you've got a lesser width rotor and they wind up configured to tuck closer in.
The other thing about the dirt track car experience you're referencing is that different wheels have the barrel of the rim tapered differently. Some are stepped to the centerline (generally newer wheels) giving more clearance, others are sloped (generally older wheels), giving less clearance and more potential for issues.
Then there's more that have thicker wall vs thinner wall, offsets and backspacing... that's why the old rule of 4" bigger than your rotor for clearance comes into question right along the borderline. Some brands and styles fit better than others when you're close.
It's also why a simple Google search of will xyz wheels clear xys brakes gives conflicting answers for identical rotor and wheel sizes... because the over variables weren't the same.