This is expected behavior. Dormant actors will still replicate to a connection once to spawn & apply the latest state of their replicated properties, then stop replicating until woken up.
A user has reported that Net Dormancy is currently giving inconsistent and unexpected results. Their original report was that Net Dormancy was preventing replicated actors from disappearing when they were no longer relevant based on distance.
This was determined to be expected behavior. However, the fact that a replicated actor will replicate the first time it becomes relevant even though its Net Dormancy is set to DormantAll is not expected.
This issue may be related to UE-62354. This is why there are two actors in the reproduction, as one is a pure C++ class and the other is a Blueprint.
This occurs in 4.20
There's no existing public thread on this issue, so head over toAnswerHub just mention UE-71652 in the post.