Coroutine Won't Stop Using IEnumerator

See my code below. I don't understand why using the string variant of Start/StopCoroutine makes everything work as expected (drains stamina on key press/hold, stops drain on key release), but when I try to use the IEnumerator version of Start/StopCoroutine the stamina drain begins on key press as expected, and continues on key hold, but also continues on key release and never stops.

Am I missing something?

 void Update ()
     {
         if(Input.GetKeyDown(KeyCode.Keypad0) && transform.GetComponent<Attributes>().stamina >

         {
             transform.GetComponent<Attributes>().AdjustStamina(-2);
             blocking = true;
             //StartCoroutine("BlockingDrain");
             StartCoroutine(BlockingDrain());
         }
         if(Input.GetKeyUp(KeyCode.Keypad0))
         {
             blocking = false;
             //StopCoroutine("BlockingDrain");
             StopCoroutine(BlockingDrain());
         }
     }
 
     IEnumerator BlockingDrain ()
     {
         for (;;)
         {
             transform.GetComponent<Attributes>().AdjustStamina(-1);
             yield return new WaitForSeconds(0.25f);
         }
     }