What is “Wordlwide point in time” ?

Windows 10 Upgrade FAQ is telling us what is it.

There you have it guys. As from now on, and to avoid any confusion whatsoever, we will make precise “point in time” appointments by using PM UTC-10 (Hawaii) as a reference time zone.

I can’t resist not to end this post without asking:  What’s wrong with GMT aka Greenwich Meridian Time ?