I find this an interesting rationale. It's known that certain blades were rejected by shinsa, but after crushing the mei, they were attributed to the smiths who were in the signature in the first place. So likely they were rejected for the mei and not for the work itself. This is a self fulfilling way of working, because over time, all the varying mei will be assumed gimei, except those in the books. So it stands to reason that this way, certain valid shoshin ways of signing will disappear because they were deemed gimei, simply because they weren't recorded in the books.