I'd never heard the term "Office GMT", but it makes perfect sense when comparing the functionality vs the "True GMT" (or, less confrontationally, "Traveller's GMT").
The Office GMT is great for tracking timezones of other people (if you are in the UK, but need to know what time it is in the US, for instance).
The Traveller's GMT is great if you frequently travel to other timezones and need to be able to quickly adjust your local time, preferably without adjusting the minutes or hacking the seconds.
So, I guess it depends on what your use case is, as to which functionality is better suited to you.
Here's a great video which illustrates the difference:
https://youtu.be/GNIjbdr2Jjw
Incidentally, the Traveller's GMT functionality isn't the preserve of the likes of Rolex, Omega and Tudor. The Seiko Kinetic GMT watches also have the same adjustable jump hour hand, e.g this rather imposing beast which I recently bought as a diving watch to accompany my GMTII:
https://www.jurawatches.co.uk/produc...un065p1-so-657