He is still part of his unit, so he has an obligation to be a part of and parade with that unit on a regular basis, at least once a month, but more often once a week. So he is actively reintegrated into his military community right away.
Upon his return, he has to spend those three half days with his unit in terms of reintegration and processing, so that keeps the contact firm there, and then the requirements for his medical follow-ups post-leave are also monitored by that unit.