As far as I know this isn't true, LFP batteries degrade more when charged to 100% than if they're charged to less, but the remaining charge can't be estimated accurately unless you do:
https://www.torquenews.com/15475/battery-charging-behavior-t...
https://www.reddit.com/r/TeslaModel3/comments/yh5ts5/m3_lfp_...
(They still degrade much less than the other kind of battery Tesla uses, however).