The only restriction on global location is the applicants accessibility for current available times of day that groups are hosted, or on access to Zoom video.
While some group day options are conducive to the Americas in the evening, which falls the next day near noon hour for Australia, or early morning for China, they are the middle of the night for the UK regions.
The reverse holds true for groups held in the morning or early afternoon for Americas, while evening for UK regions, but the middle of the night for Australia or China regions.