I think your deduction must be correct. Does yours have the "T" stamp on the body side? Mine did not, nor have a number of others seen over the years. As Peter's books tell us this was the last operation performed at H&H, I assume these rifles were never fitted with scopes.
Why so many 1944 rifles? Could it be that there was a lag period when production of the MkI and MkII scopes ended and production of the Mk3 had not come on stream? Could it be that H&H to keep things rolling, continued to do the conversions and ship them, only without scopes?
The only other explanation I can see is that they were done after production of complete No4(T)s ceased, to 'use up' "TR" graded rifles that had previously been selected in greater numbers than the supply of telescopes or perhaps just the No4(T) contracts called for. It would have made sense to mark those rifles when they were found during the routine test firings, as if they were required later for conversion or some other purpose, they could not all be tested again.
TR rifles do surface that were never converted. I have on here at the moment in the X35--- 1945 range from which many rifles were converted to T specs it seems.
Here's a photo that just showed up in another thread:
Notice that the pad screws are staked and the rifle refinished before the "T" stamp went on as the finish flaked off went the stamp was struck. The only way that could happen is if the finish was put on at H&H as we know for certain that the "T" stamp was.