Uni, in recent years, has tended to follow what WDW does. WDW bridged tickets to passes, and later Uni started doing that too (at some point after 2011 when they didn't bridge the cost). etc. (of course, now WDW has nearly ended bridging, so I'm not sure what will happen)
This hasn't been a "thing" for Uni before, because Wet and Wild wasn't "theirs", so it wasn't included under the AP at all. So now they'll either do something different and go their own way (where you would be able to go to a 2 park ticket even after using that VB entitlement) or they'll copy WDW (where if you use that waterpark entitlement, you now get a top of the line AP).
Please oh please report back once you've upgraded. And for right now, if you don't remember the TM's name, try to do so. Just in case. I *want* you to be able to upgrade like this...I'm just worried that the TM didn't actually know what she is talking about... And if it were me there now...I would make sure I have the full amount budgeted in case I had to get the 3 park.