People are doing this because Stern are producing top notch games now, one after another.

Some people are paying deposits on machines sight unseen, knowing they can move from a LE to a Premium or to a Stern Pro incase they change their mind, or just get a refund or move the deposit to the next upcoming title. Its the best way to secure a LE if that's what the buyer really wants.
There are some pretty enthusiastic Stern collectors out there now.

I expect some people will do their best to collect JJP titles one after the other as well.
Look at the Hobitt, nothing released and people have payed up etc. Because of refunds, it makes it a worthwhile choice for some to do this.

I am dying to see Star Trek from Stern. This should be a big seller as well. I expect LE models to be all sold out 10 minutes after release etc. I am putting down a deposit on one so I don't miss out well well ahead of time, and if I don't like the LE, will move the deposit to another variant.
Exciting times ahead. Hoping prices do not move anywhere for the next 12 to 18 months.....