Actually, I think the reason this "American thing" happened was because of the long lead time between US prototyping and production and shipping from China. The Chinese factories do not always build to specs, and by the time the manufactured toys arrive on our shores the company faces the choice of selling what they paid for or trash the entire shipment and eat their losses. Guess what everyone did in the end.
Most of the early McFarlane "variants" were a result of fixes to the scenario described above. They first version always had some kind of defect or mistakes that got fixed in the later reissues. They only started this whole manufactured variant practice later on when they realized there was a market for it. You don't see this practice with Japanese manufactuers because they are much closer to China geographically and usually problems are caught before the product was made and shipped.
BTW I don't think the TRU cannon fodder is really that rare. You'd be lucky if you can get back what you paid for it, as is the case with most 1/60 Yamatos.