The Closed Alpha playtest isn’t an invitation to publicly review, it’s an invitation to playtest. They’re trying to gather data and feedback on an inherently feature-incomplete and unpolished game to help with development. There are going to be private channels for feedback and the playtest data itself is like feedback so public channels are redundant. Obviously Marvel is also just trying to dodge criticism, but that’s not a mutually exclusive reason.
Denying references to other places that directly compete with you seems pretty reasonable to me. You don’t see toaster boxes at Walmart saying it’s also available at Target or whatever