Now that Striker allows creating Diffusion repos for tools, a logical extension would be to allow creating a single #Tool-<toolname> Maniphest project. That project could be associated with any Diffusion repos for the tool and would complete the git+code review+bug reporting feature set that is commonly found in 3rd party VCS hosting services.
There are some existing Maniphest projects for tools (e.g. XTools) that use a different naming convention of #Tool-Labs-tools-<toolname>. This looks like a carry over from the old Bugzilla nested organization scheme. The naming guidelines seem to favor shorter names for new project creation. An alternate way to organize per-Tool projects would be as subprojects of a new umbrella project named "Tool-Labs-Tools" or just "Tools". Input from the Project-Admins and the Tool Labs developer community on this would be useful.
Naming and organization questions were settled by T167244: Rename and update Cloud Services Phabricator projects. Projects for Toolforge hosted tools should be named tool-<name of tool> and be sub-projects of the Tools umbrella project. Vanity naming that strips the tool- prefix can be handled on a per-project basis via the normal Phabricator project management request process. Even if that is done the Phab project should remain a sub-project of Tools to increase discoverability.