Absalom
Here is the way I look at this, for whatever it is worth.
The late Victory Model (after December, 1944) and the early postwar .38 M&P clearly used the same frame and inner lock works. It is very difficult to know when the frames were actually forged, but that really doesn't matter for nomenclature purposes. After the last wartime gun shipped to the Navy on August 13, 1945, there were no more
military Victory Model revolvers. Two days later, Japan's surrender was announced.
S&W then began tooling up to return to civilian production. Of course they used up revolvers and parts that were on hand and many of those had the SV prefix. I have no doubt that there were racks and racks of forged frames waiting to be used. There were also barrels and other parts left over. These were redirected to civilian demand, including the demand for revolvers from stateside police departments. SV prefix guns were used to fill those early orders. Eventually those were used up and subsequent assembly began using revolvers marked with a simple S prefix. I don't think of any of those guns as Victory Models. I tend to use that term only for revolvers that were sent to the military or the DSC.
A revolver that was sent to a PD or a civilian distributor would be considered a postwar Military & Police revolver, even though the gun itself is largely indistinguishable from a Victory Model. Those civilian shipments seem to have begun in February, 1946, although a much larger number began shipping the next month.
Anyway, that is how I compartmentalize these guns in my own mind, and I tend to think most collectors who concentrate on this period feel the same way. I don't think it matters that they were essentially the same gun.
Edited to add: I've located quite a few SV revolvers in the SV769xxx to SV774xxx range that shipped to the civilian market. They went out the door in March, 1946. Clearly, these were left over from military production but were never sent to the military.