Assigning a guest to a particular list, folder or space etc means they only have visibility and access to that scope. But they can still SEE everyone across all spaces in the people list - including other guests!

If ClickUp users use this functionality to add clients as a guest (which I imagine is the point of the functionality and majority of the use cases) then I expect everyone (including the guests) would want their details to remain private.

This functionality is not on the roadmap - improved controls of guest visibility from guest roles should be introduced to tackle this privacy concern.