I see what you mean. Here's what's published on my side of things:
So it looks like Max. Image Size is about 12.68"x18.44" if printing on 13"x19.2".
I can't imagine it would be any different if it's boxed as Kyocera, Copystar, Ricoh, MCS, or BlueCrest.
Sounds like the MCS rep just didn't know what he/she was talking about. The Pro 15000c can feed both 12x18 and 13x19. The Standard 500 sheet Trays can store up to 12x18. The MP Tray/Vac Feed LCT can do 13x19.