UWorld::InternalGetNetMode will use DemoNetDriver->GetNetMode() if there is a DemoNetDriver, resulting in NM_ListenServer being returned when recording a replay. This seems to have been originally added to resolve some issue with IsClient and IsServer, which are now deprecated.
In a standalone instance, start recording a replay and then check UWorld::GetNetMode.
Expected: the net mode will be NM_Standalone
Actual: the net mode will be NM_ListenServer
There's no existing public thread on this issue, so head over to Questions & Answers just mention UE-168278 in the post.