Please ignore this post as I did not fully understand the Power Manager threshold settings. As a result, PM appears to be working normally. Also, I see that in the BIOS, the lowest value for the charging Start point is 50% so assume this by hardware design.
Win11  Using the Custom option in Power Manager, I've set the point where the battery is to stop charging at 90%. Initially it maintains the setting but after successive reboots, it now stops at 71%. I've tried other settings and it always reverts to ~ 20% less. However,  the Custom Power Manager settings remain as I set them. Also, I am unable to set the Starting point as it cannot be changed from 50%.
Power Manager Using Wrong Custom Settings