That's what Rta told me. If I wanted to tow it unrego'd I'd have to get a pink slip before they issue a permit. You may as well get it blue slipped instead then pay the rego fee and be done with it. There's not much difference in time or cost between the blue and pink slips.
I find it odd that the interstate builders aren't clued up with the processes their ustomers have to go thru, but I've just been thru the process myself.