I don’t think this is a real bug. I have dozens of screenshots from Netflix and other “drm” video providers (10.13-.6) used for memes. Maybe it wasn’t supposed to work with system screenshots but it did for years.
"You are not authorized to access bug 1876826."
Although judging by the title it seems like a feature not a bug.
Sorry, first time reporting on Bugzilla. But this is a serious bug that could disturb everyone who uses DRM, including Netflix.