Not exactly true. Having had a few conversations with Disney legal about this and how it works and their attitudes about it, since I am one of those said vloggers...
Disney has told me directly that as long as I am not interfering with daily operations, not violating NDA, not interfering with guests and their enjoyment of the parks or intruding upon them, and not smearing/ slandering/ making the company look bad/ etc, then I can operate on property and they unofficially will consider me there as with permission of the PR/ marketing as part of that, which in their opinions means that Disney's rights as far as video/ photography of guests applies as well as long as I do not violate company policies and/ or cross any company lines and realize that Disney can revoke that permission and access at any time.
I'm quite sure that they've said essentially the same thing to others as well. I'm small fry. So I don't have some of the liberties that many of the larger vloggers do, (and they don't cover my admissions, food, or anything else like that) but it comes with the territory. And Disney can, and does, at times say what is ok and what isn't.
Disney realizes that while I might make a bit of money off of advertising, they are getting back more than that in value from the free advertising/ PR/ etc that I and other youtube channels provide. And as such they're willing to provide essentially a quip pro quo in exchange for letting vloggers film on property.
(oh, and yes, I do normally carry a copy of said emails with me when I'm in the parks, just in case there is a question, but no, I will not provide them to you because I don't want to make them available for others to edit/ photoshop/ make use of in ways they weren't intended. Hope that's understandable)