@akonsu The reheating stage is insurance. When you go below the working temperature, you start to form other unstable crystals that effect the temper. By reheating it back to working temperature with warm chocolate in the tank, you melt those unstable crystals.
If you hit the working temperature perfectly, with the right amount of beta crystals in the liquid chocolate, you don't need to reheat it. But if you miss it, then you have to reheat with a heat gun or something instead, warm chocolate is easier but you don't have in the tank any more!
This is why understanding what tempering is actually doing to the chocolate is important, not just slavishly following rules about temperatures and heating and cooling 
(But those rules are important too lolol)
HTH
