One company using it doesn't make it the "industry" term. It was the copycats that followed like Apple and Paramount that made it into an industry term. It kind of makes sense for Paramount, but really doesn't for Apple. Par for the course for Apple TV+, barely baked content on a barely baked poorly named service.
I've watched 3 shows on Apple TV+ - Extrapolations, The Morning Show, and Ted Lasso. All of them start very promisingly (as in, the premise is good, the initial setup of actors/sets/etc. is promising, there is lots of potential ways it could go) but they're all superficial, get very predictable, and then the quality steeply goes downhill after a point. All three could have been way better, and had vastly more promise than what they delivered. It was enough to make me cancel the service.
Apple has been using + way before Disney. Apple care+, iPhone 6 Plus and I’m pretty sure they had another plus product or service in the 2000s or earlier that I’m forgetting right now. Edit: it was the Mac plus from 1986.
I’ve always associated “plus” with Apple, not with Disney.