@ankushd75501011 interesting but valid question.
As of I know, it is how it works.. since smart cropping works as part of scene7 process step in DAM asset update workflow.
If you have to prevent below usecase, try to create separate workflow for scene7 sync with that single process step so that when image gets updated for general edits these smart crops will not refreshed.
Just option try it out but with this we will loose auto sync to scene7/DM , authors has to manually sync to scene7/DM whenever needed/ondemand.