Why is Windows seeing my NAS as two separate devices (one with FQDN, the other with local name)?

• My home LAN has a Windows Active Directory domain, with the DNS name corp.example.com.

• My Synology NAS has the FQDN nas.corp.example.com..

• My Windows 10 desktop has the FQDN cube.corp.example.com..

• I am using split-brain DNS:

  • The DNS servers within my home LAN will report that nas.corp.example.com is 172.16.1.10.
  • The Internet-accessible public DNS server for example.com will return A IN 2.718.281.828 for queries for both nas.corp.example.com and corp.example.com - where 2.718.281.828 is my home router's public IPv4 address (I use port forwarding, ofc).

• Both my (Windows 10) desktop computer and Synology NAS are domain-joined.

  • Running ipconfig /all on my desktop reports Primary Dns Suffix: corp.example.com.

• Therefore I expect Windows 10 to know that nas.corp.example.com. (FQDN) and nas (single-label) are the same host.

• But Windows 10 File Explorer lists my NAS twice: first with the FQDN and again with the single-label name.

• Answer me these questions three:

  • Why is it doing this?
  • Is this benign, or does it cause issues (e.g. extraneous lookup requests, too many connections, SMB issues?)
  • How can I make it coalesce the two nodes into one?

Screenshot proof: