The proposed time zone is to drift about 1 second every 50 years. I also suspect it wouldn’t really be a time zone in the same sense as the time zones we know - it would just be a standardised calibration reference. Dates and times expressed in “moon time” would probably just be some leap second off of a known Earth time zone, and because it’s mere seconds over centuries, I think the only use of this time zone is to calculate ultra-precise time diffs between two earth datetimes when the observer is on the moon. At least, that’s how I interpret the articles I can find about it.
It’s also important for things like GPS, as related to other planets, as well as orbital maneuvering.
What they’re actually being told to build is “write down the rules for moon time”, which is basically what you said but defined in terms of “this much faster than earth time”, and a system doing the same thing on other planets or places in the solar system.
So it’s less a timezone and more a time system, and instructions for how you calibrate your atomic clock on the moon and reconcile the difference with terrestrial clocks.
Great explanation, but unfortunately the post in the image OC missed the absolute best part, the parody article.