Interesting, I guess that suggests that it is only a matter of style then.
I think nearly every other editor will generate SGFs with the parentheses removed. Earlier, you gave ease of implementation as a reason to have extraneous parentheses, however, I find that reason dubious, since it is very easy not to insert those parentheses in the first place.
About 5 years ago, it was not implemented this way. I know since I was looking at SGFs generated by OGS and reporting some bugs. I guess this change must have happened at some point after that.