The theatres where I live have started using assigned seating for the premium showings (you are able to choose from the available seats when you book your tickets).
If your theatre has showings with assigned seating (or is planning to add them), management may have simply updated the terms and conditions on all of the tickets rather than going through the process of figuring out which tickets need the additional condition and updating the website logic.
Indeed, a couple of our newer theaters have tickets that are purchased with assigned seating. Of course, the seats also are extra wide, recline, and there’s a bar in the lobby. It’s pretty sweet really.
I have to say that I also really like the new “assigned seating,” because it eliminates the rush to the theater in order to snag good seats.
The only problem is, I went on a triple-date a few weeks ago and we were supposed to see How To Train Your Dragon 2. The date bought the tickets through Fandango. Before going to dinner, we picked up our tickets from the kiosk without giving them a glance. After eating, we walked to the theater and saw we had tickets for Transformers 4. Checking the receipt from Fandango, we had tickets for HTTYD2, but since the seats were assigned, we felt like we were stuck to see all the Baysplosions, because someone else might be in our seats at our intended movie (or it might be sold out).
On another note, if you only ever have a day to live, go see Transformers 4, because that movie feels like it goes on forever.