That is PatternBatteryCharging which is active whenever device is charging. Differentiating between battery full is done via battery full pattern having higher priority than charging pattern. Which basically means that when battery full pattern is disabled / timeout expires → charging pattern resurfaces. (not sure if it makes sense, just the way it has always been…)
If you disable blinking, then it is possible to define RGB intensity values too, so something like this should make battery full = lowest possible intensity red:
printf "[LEDPatternHybris]\nPatternBatteryFull=40;4;0;0;0;010000\n" > /etc/mce/90-battery-full-hack.ini
systemctl restart mce