John, you are correct in as much as they were designed to produce castings that were to the larger scale of 1/1200 BUT moulds shrink on curing and with age, so that early castings might be longer than later castings from the same mould, particularly if the model is a slow seller. Many manufacturers produce several of the early castings to put on one side to make new moulds and these might be 5% smaller than the original master and so on down the generations.
Some manufacturers made models in 1/1200 scale and later bowed to pressurefrom collectors to change to 1/1250 scale and so "re-mastered" might also be code for "change of scale".
On ebay many sellers do not know the products and might be making an innocent mistake and some, perhaps, know that more people will search for 1/1250 rather than 1/1200...
Most of my collection has been bought from dealers that I know and trust and only about 5% has been bought from people who I have never heard of on ebay.