It was my understanding years ago that the Star Wars team that works on all the original, wide release product was separate from the team that worked on exclusives and, at the time, the 12" line (possibly other stuff).
That was indeed the way it was at the start of the line, one team based in Pawtucket, one based in Cincinatti (old Kenner), but a re-organization and office closing
between ep1 and ep2 merged everyone together (and effectively killed Kenner once and for all by closing their Cincinatti offices). Since the early 00s, it's been one Star Wars team for the most part.
it always sounded to me like different factories had different molds at their disposal.
Yep, definitely. That's why we get certain crappy characters in the Legends assortment despite there being better versions out there - it all has to do with which molds can be used at which factory. Based on the different machinery used and differnt tool styles, some molds/tools simply can't be transferred between factories so we end up with loads of RotS Chewie in the Legends line when we really want more VOTC Chewies, etc.
There isn't one set factory for exclusives though. They are just run at whichever of the factories has the time to run them to meet the timeline of the retailer. I wouldn't say that exclusives are "forced" into using only old molds.
I'm just guessing on a lot of this based on info that I've read about from various sources over the years, but would love to know if there's some logical reason for some of these decisions or if it's a coin flip on the factory end or what. I'm sure there's a cost factor to this, as in what's the cheapest mold available to press out an exclusive, for example. What one will make Hasbro the most money, still offer a good exclusive product for a retailer and balance all that with a retail price that consumers will pay?
I think the last part is a big concern for them right now. I have no doubt that "cost" is the biggest reason for a lot of the decisions lately.
It may well be that the "newer" vintage Speeder Bike sculpt (the one with the corrected handle bars) has a tool that can only be used at a certain factory. It could very well be that in order to meet TRU's wanted timing for the product and in order to meet a certain desired price point, they had no choice but to use the oldest Bike Mold since that "fit" best.
That kind of decision happens all the time - exclusives, repacks, Legends, etc. Plenty of times in the history of the line, the cheapest alternative got chosen (CommTech Han) instead of the best choice (VOTC Han) and that was 100% due to costing goals.