Granted, it was a reissue, but (one of) the Princeton Reverb amps I had came with a 12... and yeah, everyone seemed surprised by that. I really don't know whose idea it was, but it came from Fender that way. Offhand I would guess a larger dealer ordered a special run of them. It was also tweed covered, so there's another clue.
At 1:35 in the video, RT says "...Fender is making awfully good amps these days. It might be possible to take a new Princeton Reverb, and do this [meaning the Bear mods I guess] to it... and have a great amp." He goes on the explain that much of its sound is owed to the 12" in JBL over the 10".
So that was just one takeaway. The other, more interesting thing was the addition of a Mids pot to the tone stack of the Princeton. That could make all the difference.