Just out of curiousity was did this happen Friday night? (yesterday) on the YYZ-YXU flight.

Sounds like one of the new concierges that they've just hired. Being protected on a flight generally means a seat is blocked in your name. If not, you are just added to the Waitlist (which is like half protection depending on your status).

The reason why the concierge couldn't give you a seat number (or didn't) is because the A/C was oversold, and hoping for misconnects you would have priority for a seat over everyone else (minus the MMers). I have seen YYZ-YXU flights be oversold by up to 5, and YYZ-YOW being oversold by up to 13 and the misconnects made it so that everyone that wanted a seat, got one. AC does employ sophisticated analytics to oversell by a certain margin to prevent IDB compensation and maintain full fights.

If you had access to flightstats you probably would have seen the flight availability being Y1 or 0. I would have asked to have been put on another flight, or if the last flight out, ask to be comped for a one way rental car or hotel room.

One FTer that reported a VDB on a YYZ-YXU flight made like a bandit with a hotel room, meal vouchers, and a generous travel voucher (for such a short flight).

I once flew YYZ-YVR-YLW and misconnected in YVR for YLW and got protected on the next (and last) flight out for the evening when I went to the MLL. It was oversold but I did have a seat placement.