That report made it seem like there was multiple media members present. if the story was true it wouldn't make sense other wise. I mean, if you've got a short list of media members allowed access than you're surely going to know the Patriots cameraman isn't among them, right? We're also talking about the SB here, and teams know the media wants extra access for the big game. If you ask me a walkthrough in that circumstance (a bunch of media present) is more for casual practice than anything.
Again, if the Rams had anything of importance included in that walkthrough they would have made it private, and NE's cameraman wouldn't have been allowed access, even without a camera in his hands.
PS: let's remember there hasn't been a shread of evidence backing this story, yet.