The comments quickly filled with "experts" saying what they are doing is illegal. I'm no expert, so this is my opinion.
It is private property, so access is granted with conditions.
It all seems reasonable to me, if you don't like to rules, don't visit. What isn't clear is how prominently they are dispalyed as you walk through the door. Which I think is more of concern. But everyone seems focused on how pictures might be used, not if people could reasonably be expect to know what they were agreeing to.
Other venues have similar restrictions, concert and theatre venues ban photography.
The "experts" also say you have to sign a contract for it to be binding, I don't think that is true. You don't sign contrats for software you install, or for tickets you buy. Just because no-one reads T&C's doesn't mean they can be ignored.
I am sure there are plenty of instances where proceeding with an action infers acceptance of T&C's.
The T&C's that visitors agree to by entering the building don't say you lose ownership of your pictures. Or that if you are seen taking pictures the company can ask you to delete them or take the memory card. They have been changed, here is a link to the original agreement.
I suspect that the commentors haven't followed the link. Even the writer doesn't appear to understood what was written. Neither version seized ownership.
It says you agree to allow the building owners to retweet, or reshare your social media posts. I guess the actual wording doesn't make such an attention grabbing headline.