Other film transfers might be done from internegatives made from the interpositive, or from low-contrast prints . . .

The thing is, nowhere in that quote does it specifically say that they are talking about previous releases of the SW movies. "Other film transfers" simply sounds as though he is referring to practises used on home video transfers of other movies altogether, and not the SW films at all. So there's really nothing solid that can be inferred from this about where the previous releases came from, or why some were missing the burn marks or any of that.