I thought maybe when they say 'square' they mean not round as in the fisheye 110 camera. The Orca and Color Tiger films are pre-exposed to the 13X17 rectangular format.
What do you mean by pre-exposed to a rectangular format? They certainly don't expose frame boundaries in the film do they? They probably expose the film number and such things. I expect all roll film to have a continuous sensitive surface. I mean, just like you can take 4,5x6, 6x6, 6x7 and 6x9 frames on the same 120 roll film, or just like you can take 24x36 or 24x18 half-frame pictures on a 135 roll, you should be able to take 13x13 and 13x17 on the same 127 cartridge.