First off, using your phone till it dies or reaches 0% is bad for lithium ion. Try to keep it >20% if you can.
Optimized charging works only when you charge your phone the same way all the time - and leave it on the charger for long periods of time. If you do this, then it will only charge to 80% and then hold it there until an hour or two before you usually unplug it, then charge it to full.
The idea is that keeping a Lithium Ion battery between 20-80% extends the life significantly.
If you’re like me and plug your phone to charge all the time (my car, work, home, etc) - optimized charging will never turn on.