My intention was to buy time and follow up with an image of the first page of the MWO - but my 'piling' system has thwarted me yet again. Though nobody has turned up any sort of report tracking WWII progress on MWO-3, anecdotes from ETO unit histories (usually in Feb-Mar 45) establish that the process was initiated. With MWO-4 and -5 not coming until after VE-Day, there's room for carbines manufactured with flip sights to have adjustables - but retain their original mag catches and front bands (and not necessarily limited to the ETO).
With the early postwar chaos involved in the rush to peacetime normalcy and the massive budget cuts, I don't find it hard to accept the possibility that large quantities of carbines remained in the crates they rode back home in. Claims that almost all carbines were rebuilt post-WWII universally fail to include any support. Would be nice to find the hidey hole with the progress reports.