Some IC hotel's + some golden keys concierges at IC hotels have a very active whatsapp network.

If one would to casually mention their next destination,
and there is a reason for ..... (recognition, VVIP, service recovery, special request, any reason fill in the blanks)
the first hotel / department of the first IC hotel will inform the other IC hotel

My examples:

IC Bali Jimbaran seems to be in good contact with IC Grand Parnas Seoul
- impressive welcome.... my first visit to the hotel and they all know my name....,seems i was registered as VIP and forwarded from Bali to Seoul

IC BKK
- when stepping out from hotel arranged transfer transport, addressed by name when stepping out
I believe the driver txts or calls the hotel to warn of my impending arrival

IC Parklane London
- all the doormen seem to know me as soon as i alight from the black cab
..l. maybe because i emailed in advance to reservations my estimated arrival time and they keep track of time
...II..... maybe they don't forget my face since last time because i know Atacama40 .... so unforgetable on the watch list or the YIKES! column...

IC AMS concierge seems to know IC MIA's concierge very welll (both golden keys)
So not a warm welcome upon arrival by doormen but actually by the head concierge


So yes i guess the cause is facial recognition, modern whatsapp technology, internal IHG communication grid, very observant service oriented staff..... a dash of MI6 / AIVD / CIA / Mossad or just being a guest like DonPedro with impressive stature & personality

eein : indeed at that specific hotel it is exactly as you have mentioned .... pretty smart way
unfortunately they gave my twin brother quite a fawning untill i stepped in at the club lounge too