Because of the additional script in the header, there is no "flicker" when you go to different pages.
However, when theme settings are updated on another device, it needs to pull from the member JSON. In those times, there will be a slight flicker which will only happen once.
This is just one example of how you can use member JSON to do some really, really cool stuff.
If you want to check out more examples, check out our MemberScripts library!