I think you've hit the nail on the head: any module can be listed as "under active development" as long as the maintainer says that's so; unless there's some sort of manual intervention by a user with appropriate permissions on d.o.
From the Dealing with unsupported (abandoned) projects page:
While most maintainers continue to care for their projects after the initial release, some need to move on and leave the project in the care of the community. Ideally, maintainers will put up a note that the project is in need of a new maintainer so the work can continue uninterrupted. Occasionally, though, a maintainer will stop maintaining a project without explanation.
The page goes on to explain the various routes you can take to either take over maintenance of a module that appears abandoned, or report it so that it can be reviewed. It's not a particularly quick process (the advice is to wait 2 weeks for a response from the current maintainer before continuing), but it's probably your best course of action.
I realise the specific phrase "under active development" isn't mentioned in any of that, but I think it's pretty much the same deal.