Good point - now thinking about it. Not on mine, nieces apparently did theirs while on roaming free on TW Mobile & SKTel with their iPhone 6+ (running iOS 9, possibly with the WiFi Assist ??) - they're mostly on a faster 3G connection & kept it brief ... aren't sure if some of that was on fast WiFi networks in the hotel - I know that on my 5s, the Seoul Novotel Ambassador's broadband benchmarked at 115MB/80MB speed, pure joy to do things on that connection.

It's very possible that they're not on cellular data but doing that over WiFi data on the hotel's network. Initially, they couldn't connect & they had to call T-Mo & something was switched on/enabled & they're good for the remainder of the 2 weeks trip.