Actually, now that I think of it, I've received stock distributions before, but never paid this sort of attention to it. For example, when Wendy's spun off Tim Hortons, the Wendy's stock traded at its pre-split price right up to the distribution and only fell on the day that the distribution hit my account. There may have been a without distribution price, but I was totally unaware of it, if so.
So really, there's nothing unusual about trading in CY transferring the rights to the distribution, as well. The main difference from WEN is that the spun-off company is already trading.
BTW, both WEN and THI prices went up following the distribution. For similar reasons - the portfolio effect - that many of us have been expecting from CY post-split. As far as CY is concerned it's hard to see how it could fail to go up after 9/29 if it's anywhere near $3 the day of the spinoff.
Allow me trying to rationize it. Because there are lots of CY holders shorted SPWRA, because there are lots of CY holders waiting for distribution day to sell SPWRB, so SPWRA is under buying pressure and SPWRB will face selling pressure. Consequently on the first day it becomes available to sell, SPWRB will open at somewhere $75 providing SPWRA maintains today's closing price. Then CY WI will open at around $5.