The windshield washer tank is in the fender, with the widebody, there isn't lot of space left. They can't reuse the tank from the regular integra. I guess it's a cost related question to do not develop another one with sensor.
Did you buy it directly from the PRL website ? I saw someone on Facebook saying their website has the part incorrectly listed. You get the FK8(Civic) part when choosing for ITS. Mine is ok.