Well, I don't know how to explain it any other way. I get what you are saying, yes, they could have done it before - but now that dogs are allowed by anyone, it just put a great big spotlight on "hey, I can bring our dog!" It's a lot easier for people to abandon their morals by degrees - and that dogs are now allowed for everyone, and six words can save you $350/week, it's going to put thoughts out there that weren't before. It's just a little "fib" now, and since dogs are allowed period, they don't have to fear standing out.
Those dogs aren't necessarily going to the parks. I doubt they will. They will be left in the room or taken to the kennel. If you think Disney is going to question them further, have you ever been to WDW? LOL. Employees are terrified to question guests over anything - and the fear of a lawsuit is so high that they aren't going to be instructed not to dare. "Why was he in your room all day?" "We only have to worry about our health problem at night". Not that it ever would get that far, LOL.
It's just as easy to abuse as GAC, and since you just have to lie once at the front desk when you check in, it's actually a lot easier.