Take this image. Try moving the tasks from Milestone "2024-07-10" to Milestone "Neeeext, using using the feature Move Tasks to Project:
What happens
If you select a "Milestone Project" as destination, it does not work:
You must choose a project with a workboard
Expected result
It works. Tasks are moved to the selected Milestone Project.
Note that since a Milestone is technically a project, I suppose this feature must work, using the button Move Tasks to Project. But note there is also the button Move Tasks to Column (premising that this feature does not work there either).