It currently uses the "<None>" template's settings instead: Line Weights are not kept, Clouds from multiple Revisions get combined into one, etc. ...
NOTE: This usually is a non-issue as the main reason to save out a View or Sheet is to then insert it into another project (which would overwrite the Line Weight settings anyway). However, the result is unexpected and should be changed (you would expect saving a view/sheet to give a result similar to deleting everything else and purging, NOT copying the selected view into a new project using the <None> template).