published-adventures is not only used on questions with tags for the specific adventure; see Where is Sturnheim?, for example.
One example, though, isn't much of an argument, so let's take a look at 160+ other open questions about published adventures outside of D&D 5e. (D&D 5e being the place where we've most-commonly seen individual adventures' tags.) Given that many questions, I think the correct frame to approach the tag is not "do we need it?" but rather "is it doing harm?"
The harms of a meta tag include:
- acting as a "tag-tax," crowding out other, useful tags
- communicating "secret information" that wouldn't be obvious to newcomers, causing friction with established users
- placing restrictions on an answer, rather than describing the content of the question
I don't see any of those happening here, personally. I took a quick look at the list linked above, and very few (maybe a dozen) of them even have 5 tags on them. We haven't seen metas trying to clarify what is meant by published-adventures. And we (or I, at least) haven't been having to clean up lots of back-and-forth comment chains where the tag is causing friction between questions and answers.
(Though I'd be glad to learn if I'm wrong, so that we can do something about it. Speak up if you see evidence contrary to what I'm describing!)