I had it up to 100% indicated only once after a long steep downhill at 25 mph on cruise control. Otherwise in 20,000 miles, I've never seen it that high. The other circumstance where it seems to charge high (over 3/4) is when it is raining. High load on the car, but not really a need for added battery torque like going up a hill. So the engine stays on for a longer period, the engine is charging, but no battery juice is added. When not raining, the exact same terrain will put the car in EV, which keeps the battery about half full.
There isn't any particular benefit in having the battery charged to 100% indicated. In fact, battery life will be highest with the exact same algorithm that the engineers used - keep it at about half full.
2018 Kia LX HEV Metal Stream with Advanced Tech