The loophole is they don't use "Marvel" in the name--it's "Super Hero HQ" (that just happens to not sell anything DC).
Tho you are correct, Springs is not a "theme park" per the contract. But IIRC, it's been a minute since I read it, using the word "Marvel" in any sort of promotion is prohibited, or at least a grey area. Even for characters they own--don't expect "Marvel's Guardians of the Galaxy" in EPCOT. They also want to avoid any appearance of the store being akin to the Planet Hollywood rip-off Marvel was contemplating in the 90s.
FWIW, I think Comcast's lawyers are good enough they could shut down that store in a day if they wanted to. There's a fair amount of play in the contract, and it's weighted toward UOR. But if your Distinguished Competition wants to sell merch promoting your #1 coaster, why stop them? Now if the Avengers popped up in The Void, different story entirely...