I don't remember what I was thinking while I was writing that. Fortunately, I do remember that I was trying to populate a large number of tags, so the rest of the wording provides enough information for me to deduce my thought processes.
For questions regarding MS-DOS, the Microsoft Disk Operating System.
This tag wiki excerpt doesn't really give much guidance as to how to use the tag. Is there anything that isn't the OS, but is in-scope for this tag? Oh!
For questions regarding MS-DOS, the Microsoft Disk Operating System
., and its batch scripting language.
But other DOSs had batch, didn't they? Questions about batch in general should be tagged dos, not ms-dos.
Do not use this tag for questions about DOS batch languages in general.
Pretty sure there was nothing more to it than that. There aren't many questions about batch, and in retrospect it does seem a fairly obvious thing, so it probably doesn't need to be described explicitly. (I believe this was around the time when there was some inconsistency around Windows tagging, so I felt the need to clarify.)
There are questions about batch that would be on-topic, I think, though most relate directly to how the OS handles it; again, something you'd obviously use the OS tag for.