When using mesh modifiers in MOOSE, the subdomain of refined elements might change such that several refined elements born from the same parent have different subdomain IDs.

WHen coarsening, it seems to me that they could be merged, which would be an issue if:

• the variable we need to re-initialize after is not defined on all subdomains

This is my current explanation for idaholab/moose#29699, after we solved two other problems in moose