I will look into it, but there has not been any changes in regular "open with" after the bug fix for open mishandling of an app's command line parameters. Perhaps that is having secondary effects? I have always Apple/Command-Q out of apps when using normal "open with"after finishing editing. I thought that is what all "open with" users on Mac would do. So I have never see an issue with BBEdit.
Here is that bug fix:
https://github.com/Sigil-Ebook/Sigil...61cf9eb3746e28
Using --args is correct syntax for macOS open.