Stopping to check for good balance is an excellent exercise. Yes, when you're dancing 'for real' ,the body flight would make this impossible, But body flight can cover up, to some extent, lack of control and balance (i speak from first-hand experience!!)
Similar techniques (i.e. practising at different speeds, even very slowly)are used when learning to play an instrument, and for the same reason - to develop good fundamental technique. If a dancer CAN'T stop with good balance at the end of a feather step, then there is a problem