Good possibility. The limited historical data I can see on flightradar24 shows it been a 737-900 on all flights, and the seat map view in the app matches that, but my dates are far enough into the future not to show up yet on flightradar24.

Not yet; I've just taken the language saying that they do it can as their reason why. I doubt they'd give me an idea of how often this happens. But I might call now, thanks.