Last I was aware of the Orientation Island presented new users with four choices, normal WA, Sandbox, and two private entry points.
Those who choose normal WA enter at the junction of 4 sims dedicated to the the new users experiece, spreading the avatar computation load over 4 servers.
Those who choose either private entry point all go to one server, and that server is running not only the new arrivals, and in the case of the Shelter, serving as the local telehub as well, but also running the whole rest of the privately owned parcels in the sim.
This inequality of burden on the servers may skew the test results.