cell phone batteries

"As of February 18, 2027, user-replaceable batteries should be included in all smartphones and tablets sold within the [EU] bloc. The relocation is part of a bigger initiative to lessen electronic waste and prolong the lifetime of consumer devices."...

Is there a known mechanism by which holding a cell phone in your hands could cause the batteries to apparently have an increase in charge? This "increase in charge" is indicated by the "battery life indicator" going up from say one bar to two, or two bars to three. The cell phone starts out...