That's the thing though: it isn't released. Sideshow sending that email around is probably a tip-off of the waitlist being long as hell (60%+ of the edition size/around 300). These things definitely tend to sell better after the buzz hits with in-hand photos as you said, but the email coupled with the fact that the reg is still up is definitely more indicative of Sideshow seizing the chance to sell more regs than this being something crazily desirable.
Oh I def don't deny that is what Sideshow is trying to do, from a business perspective it makes sense for them to make a logical assumption in regards to certain waitlist orders not being likely to convert and letting those folks know in hopes of having them preorder the reg edition. On that note it's actually a win for the consumer aswell...if I really want a statue and am on a waitlist for the EX, I'd rather know if I had a chance or not before the reg edition sold out. I guess I see it like a win win scenario as long as the unknown formula for determining where the cut off is for the waitlist holds true. That really is the missing piece to the puzzle. What is the process for determining where the logical cut off is for a waitlist and does it hold true to real world demand.
Every situation is unique so guess well just have to see how things play out. If after a statue is released we see it go back into "In Stock" status, then we will for sure know that the logic behind the waitlist cutoff isn't working as expected or was purely intended to sell out the reg version. If that situation doesn't occur, then their process is working as expected.