I've noticed that, too. Since we upgraded to NSX 6.4.3, VLAN is set to "none" for all newly created logical switch dvPortgroups.
But it seems that this is not a bug, because this behavior change is mentioned in a KB article for another problem: VMware Knowledge Base
In NSX for vSphere 6.4.0 and above, logical switch portgroups have VLAN configured as None.
Good find. Thanks. We don't see any network traffic issues among the VXLAN-connected VMs, so I was curious if something changed in the backend.
Could be an annoyance per the KB says if you don't allow untagged network traffic on your switch ports that connect to your ESXi hosts, and you have health check enabled.