It's not unusual to see organizations making a play on words or type/font using their Greek letters in place of Latin letters. I would think it's up to each individual organization to decide if they don't want their letters represented that way.
If some overly academic person is stressing out over a t-shirt that "technically" says "As Good As Gthld", then they have too much time on their hands or simply don't understand how to be clever in graphic design.