He's still not quite sure how he feels about Mary following the recent changes and whether he trusts her assurances or not, so she gets a somewhat reserved smile in response to her wave, without the usual flirtatiousness. To be fair, despite the obvious potential for flirtation given the subject of the group, he's actually trying to take it seriously rather than as an opportunity to find other people to sleep with.
(Even if he can't help being just a little curious about that side of things with Mary, given that he knows that what he's seeing is not her true form.)
Being Jack, he does stroll over to speak to her. "So, are you just here to observe or do you actually some polyamory issues you need resolving?" he asks dryly.