I think you're right. From a business perspective, it doesn't really make sense to make one version of a statue much, much better than another version when you're charging the same price for both. I definitely think international collectors are part of the reason, but not the sole reason; it's also very likely about their retail network, expanding the market to new collectors, and minimizing the presence of the secondary market. Putting out a vastly inferior, or just incomplete version of a product hurts all of these areas for reasons that are self-explanatory.
Collectors greatly overvalue EXs as well; it's their prerogative to do so of course, but it's also kinda funny, and this is coming from someone who orders everything directly from Sideshow. All things (price) being equal, sure, the EX is a no-brainer; but I've rarely seen an EX that, IMO, is worth a $200+ dollar premium, and I think collectors paying those prices do it just to say they have the EX and to tell themselves that'll it'll be easier to sell later, even though they've already bought at a higher price point and will have to try to force the price even higher to make money, should they decide to sell. And one of the ironic things about long sold-out pieces is that you'll tend to see exclusives surface MORE, because the perceived extra liquidity that comes with the EX makes collectors more enticed to move their EXs to generate cash. And habitual flippers gravitate toward the EX naturally, whereas many collectors who "settle" for regulars do so with the perspective that they'd better be buying "for keeps", so they end up staying in collections longer. It's an interesting phenomenon.