This chawan certainly has a rather unique, medieval appearance to it and after combing through multiple references, I did not come across anything described in this particular way though I suspect the term Iga-Karatsu likely predates this pot. I can't say I know exactly what the motivation was in the description of this teabowl but I am sure that Tsukigata had his own rationale though not having ever seen another pot quite like this, I wonder in the end if this was the ultimate goal or a random series of fortuitous events. I suspect we, well I may never know unless another chawan, mizusashi or vase shows up tomorrow with the distinct hakogaki; IGA-KARATSU CHAWAN, as one can guess, stranger things have happened.
P.S. Thanks for sending the catalogues!