Screen power draw and battery capacity scale as the square of the linear dimension. They largely cancel out.
However, all the other hardware are a fixed size so proportionally large phones have longer battery lives.
I say this as someone who clung onto his 1st gen SE until I got my current 13 mini
Like internal component can be rearranged to an extent, and battery is a tradeoff, but the panel need to be one on the market, no demand, no panel
Screen power draw and battery capacity scale as the square of the linear dimension. They largely cancel out.
However, all the other hardware are a fixed size so proportionally large phones have longer battery lives.