Optimized charge requires Low Power Mode ON

I have tested this repeatedly and I can conclude that in iOS 13 on iPhone SE1, optimized charge is triggered when the Low Power Mode in On.

i turn LPM on when plugging in the phone at night, regardless of battery % (20, 40, 60%)

Next morning, battery graph shows that optimized charge occurred.

if Low Power Mode is NOT enabled, the phone will charge to 100% without optimization.

Hope this helps those of you who like me struggled to understand this neat feature.

regards