Crash seam: the planned null-Snapshot OnDataChange (no SupervisorStrategy fallback needed).
Seen RED with T6 reverted: InitializeCount 1, not 2 — with a preceding ShutdownCount>=1
assertion proving the restart really happened, so the red is not ambiguous with 'never crashed'.
Seen RED against a T3-reverted build: all 4 failed, Created[1].SubscribeCount == 0
on the headline case. 20x isolation run green after the fix was restored.