Francesco Poli:
Please help me understand, in case I am completely off-track.
You are off-track. This is not an mdadm bug. There is nothing to fix in mdadm for this. This is not a systemd bug. There is nothing to fix in systemd for this, either.
Francesco Poli:
Unfortunately, checkrestart does not suggest it.
This is not a checkrestart bug even. There is nothing to fix in checkrestart for this ...
https://anonscm.debian.org/cgit/collab-maint/debian-goodies.git/commit/?id=aed5839eb8511eade953b82dd80dd8c855cc4f42
... because it is fixed already, over a year ago. You are using debian-goodies version 0.63 or earlier. Upgrade to debian-goodies 0.64 or later.
