I don't think they were advocating for using UTC exclusively, just identifying their own timezone relative to UTC when communicating with someone in a different hour. For example: "I always eat breakfast at 08:00 UTC+01, so I prefer to do that Skype call we planned at 09:00 UTC+01 at the earliest. Is that fine with you or do you have plans in the evening?"

If you're not in UTC+01, it's easier to work out what time that would be for you than if I said I wanted to have a tele-meeting at 09:00 CET.