While I do not consider myself an "expert" on how Targets are run by ANY stretch of the imagination, I have been able to determine the following:
Target and its employees are slaves to the DPCI numbers - if there is a shelf tag/peg tag that has a number/bar code and that space is empty AND the computer says they have more of that item in, they will restock the peg/shelf.
Grevious' Wheelbike, the Droid Tri-Fighter and Obi-Wan's Starfighter ALL have the same DPCI number as the Preview Anakin Starfighter. I have no idea why, perhaps its because the UPC barcodes on the packaging are all the same or all in the same sequence? Nevertheless, Target assigned it the EPIII Assault Vehicle asst the same DPCI as the Preview Starfighter.
Same holds true with the Galactic Heroes assortment. It's one DPCI number that covers ALL of the waves. This morning in the same Target where I found the vehicles, they have eight pegs for Galactic Heroes - all of them were full of the ROTS and Bounty Hunter waves. Last week, they had been empty.
This is why Target is leaking these items at stores all over the country -- because their inventory systems are telling them to restock the shelves.
I'm pretty sure the Collection 1 figures have the same DPCI number as the preview wave, so as soon as the Preview Wave sale/discounts end, don't be surprised to see those figures start to leak out early too.
Also - I do think it's stupid that the Droid Tri-fighter is only one per case (if that is true). Gotta have a "bad guy" to dog-fight with. It would be like putting out assortments of OT vehicles and the ratio was 2 X-Wings for every 1 TIE - IMHO, that's backwards! However, I think like a fan and not like a toy line manager - the "Hero Vehicle" will always sell better than the bad-guy because most parents are only going to get their kid ONE ship, not TWO.