So you're saying it doesn't work? Last time I checked, people were being greedy as fuck during boss fights and not using vials despite being at <10% health. Why do you think that's the case? Why do you think they don't replenish their health? Because _they're greedy and they don't want to "waste" vials unless you know you're having a good run against the boss_.
The system works. Spouting anything else regarding this is utter nonsense.
Lessons to 'git gud' from the guy that breaks controllers.