No it is not your case, I said late blocking has to do when people are posting movements for the same material. Late blocking will not resolve issues when somebody blocks the material with MM02.
From my point of view is ongoing material maintenance not a usual approach. Of course it can happen that some fields need to be changed occasionally, or the material has be extended to a new plant, but this should not really lead to daily issues for WM postings
Have you already analyzed what the people change in the material master, maybe they just use MM02 instead of MM03 when they display the material master