Name one time when the test seat was a GO but the ride was a NOGO.
(and not when you had people smash the restraints for you)
They may turn away faster, but if the test said GO then you won't have issues.
It's the NOGOs that try anyway that spend 5 minutes trying to get a GO on the ride and end up with an uncomfortable experience.
If someone want to test the limits, do it when not busy.
But honestly, I've seldom seen big guys use the test seats. Normally it's kids or females.