I would say yes as it defines the time period of its use and extends the time period into which the model can be used ...... i.e. 1980 to 1987.
If you go this way then I would point out that it might be worth considering that the fume extractor changed too. So , in basic terms it’s the earlier L11 main armament with no MRS shroud with a bulkier fume extractor and with MRS fitted a thinner fume extractor. The change of fume extractor was not connected to the MRS just a small upgrade that happened to coincide. I can supply photos if it helps.
Also, just one small detail. With the thermal sleeve .... to be fitted correctly there is an asbestos strip on one side of the sleeve . The thermal sleeve should be fitted so that the asbestos strip runs parallel with the Co-Ax. This was for when the .50 Ranging Gun was fitted to protect the thermal sleeve. Even after the .50 was removed we retained the same thermal sleeve. The Britannia 20mm has it correct , but then goes on to spoil the model as the two tow ropes are way too short.