Of course he is, I agree. He’s also the second longest tenured coach at Purdue. He became a Purdue icon and was never a head coach again. Not a great comparison.
You didn't list any exceptions to your "rules" for being termed a Boilermaker and Coach Keady would not have fit under the original limitations you provided that someone who "neither attended Purdue or played for Purdue" was not a Boilermaker.