Why would Lex even know who Clark Kent is for that matter let alone make a big deal of him meeting Bruce Wayne. Weird.
Exactly. We as the audience should be saying "OMG they're finally meeting," but why the hell would Lex. I never got the impression that Clark was this famous reporter and that him meeting a celebrity would be this big tabloid moment but the BvS trailer is certainly suggesting that that's how we should take it. Otherwise Lex himself is just having a "fanboy" moment which makes no sense at all.