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.
TThe machine paper size max 12x18 single, duplex if you add the side air feed paper deck
That will print 13x19 but will not duplex 13x19 only single side.
There is a new version machine coming out soon my Kyocera contact said 15050c.
I am going to wait on the new version models talk to Ricoh and MCS.
As the more people I talked at Kyocera, Kyocera does not have a production support group in place
They are just cross training desktop printer support people.