SMB Mount despite being connected to local network (MacOS 13.7.1)

I’m flabbergasted by an unexpected SMB mount on my MacOS. Here the situation

1. I’m not connected to my local network (actually in a hotel connected through a vpn to the internet, hence not even the IP range is anywhere similar)
2. I noticed my nas being available in the finder. The SMB ports are not forwarded by the router at home. The router has a DSLit IPv6 address, i.e. no (static) IPv4
3. I can actually access the files on the nas, so this is not a ghost from the past or pure metadata cache.

I have no idea how that works! Unfortunately MacOS is terrible in getting information out. Here a few things I’ve tried, especially to try to pin down how my Mac is connecting to the (very) remote nas

dscacheutil -cachedump -entries nas.local
Unable to get details from the cache node

dns-sd -B _smb._tcp
Timestamp     A/R    Flags  if Domain               Service Type         Instance Name
17:19:55.433  Add        2  17 local.               _smb._tcp.           NAS

dns-sd -L NAS _smb._tcp
Lookup NAS._smb._tcp.local
DATE: ---Wed 20 Nov 2024---
17:21:39.439  ...STARTING...
17:21:39.628  NAS._smb._tcp.local. can be reached at nas.local.:445 (interface 17)

The local IP address of the nas can’t be pinged. Request timeout for icmp_seq 0

If anyone has an idea how the mechanics work, I’d be very interested in understanding this!

Cheers,
U