@drahardja

In this case (!) ;) this might indeed be an issue of ActivityPub as Tombstone is underspecified here.
https://github.com/w3c/activitystreams/issues
Currently Issue Triage is super active https://www.w3.org/groups/cg/socialcg/calendar/

See also feps @silverpill
https://codeberg.org/fediverse/fep/src/branch/main/fep/76ea/fep-76ea.md
https://codeberg.org/fediverse/fep/src/branch/main/fep/171b/fep-171b.md