And thats not a valid reason. Thats what they want to use and legally interpret - but I believe the consensus (from a legal perspective) is that anything that fails for a class 3, is also disqualifying for sport as in 61.53. Here is the original 2004 LSA sport letter.
Dr Chien wrote many years ago about it as well I believe saying the only difference is the "standard" of which its applied - one is the FAA, and in the case of the other it would be your local physician (sounds like Basic Med, but it isnt). But I think most postulate that anything that usually disqualifies for medical, their physician probably wont sign off either.
Now, as for the people flying under Sport - guess what ? They are not going to ground themselves over said disqualifying condition because its their avenue to fly. Just because they are flying under sport - doesnt technically mean they are legal to do so. The difficult or expensive SI notwithstanding.
The FAA 15 disqualifying conditions are for all - they dont exclude light sport. The only flexibility is the determination of "safe" standard. But as others have pointed out - that also usually involves a physician - which Im sure the Sport people are also choosing to ignore.
Earlier POA discussion of LS
I hear many times that if one knows they can't get a medical, they shouldn't bother and instead should go Light Sport. I also know that Light sport has some requirements. If someone knows they can't get a medical, isn't that supposed to be a self ground for LSA too?
www.pilotsofamerica.com
Look - you can read between all the lines you want. But the reality is its pretty clear - just many are choosing to ignore it because its convenient to them. And again - the intent wasnt there - they wouldnt disqualify you from LSA for a faileed medical if you could pass Basic Med or self determine you to be safe. The only thing they have left open is the determination of that condition and the medical standard - it isnt that "oh anyone can fly LSA if you never failed a medical, have a drivers license, are BPD with psychosis, severe depression with Suicidal ideation, stage 4 cancer, 7 heart attacks with 95% blocked arteries, etc - but self certify they are safe to fly.. doesnt work that way. The reg still applies.