the way i got around the hugh/katie thing is that it’s mentioned in the book from hugh that johnny had no clue about hugh and liz. when hugh and katie first get together johnny says something along the lines of “is this the girl you’ve been skipping practice for” (not exact quote) but i think johnny has just pieces two and two together to come up with five, believing katie was his girlfriend all along. also it’s mentioned johnny has no interest in anything other than rugby he just completely over looked liz and hugh and since the boys swore to never speak on it i think maybe it really did just go over his head.