Not really too far out an idea. At that time, the Army was in the process of finalizing the 7.62 NATO design, but Winchester had preliminary data. I don't think it is too far fetched to think that they might have produced receivers with the information they had (mainly for feed rail design) and then set them aside, waiting for the final specs before producing completed rifles.
Pure speculation, of course, be it noted.
I will say that there is some kind of idea among collectors that gun factories, whether government or private, go off in the woods with an ax and cut down a tree for a piece of wood. Then they buy a steel bar, a chunk of steel and some springs and screws, and make a gun. Then they head for the woods again. That makes things nice and neat and the "experts" can say that such and such a gun was made at 11:20 AM on the 21st of October 1893.
But factories don't work that way at all, so the idea of making receivers at one point but not building the rifles until months or years later is not at all far-fetched.
Jim