It allows them to test out at a normal level at fight/test time. I assure you, their levels are far above normal in the preceding weeks and during training due to the shot schedule. The shots are administered in dosages that peak their levels for a few days to a few weeks. Then, those levels slowly taper off. Look into the explanations of some of the failed tests recently and you will see plenty of situations where the test was given at a time when their levels were still above normal.
And the piano, it sounds like a carnival
And the microphone smells like a beer