If you didn’t want to accept the charge tolerance why did you buy it?
Where did you buy your Xtar MP1S from?
I like to be closer to 4.20v myself. I understand tho that my preference does not change the accepted tolerance.
If you can solder buy a few $1 tp4056 CC/CV li-ion charger boards. Ebay search. HKJ review. Give away ones that aren’t close enough to 4.20v for you. You could even put the tp4056 board into the shell of a Xtar MP1S or other charger.