F1 engines are normally aspirated, spark ignited, otto-cycle engines. Thus, in order to produce maximum power, they must run at near stoichiometric air/fuel ratios. More specifically, their ultimate (thermodynamic) power output is limited by the mass flow of fuel they can combust efficiently. Which in turn is limited by the mass flow of oxygen the engine can trap within the cylinder during each cycle......just how does this benefit combustion exactly?
So the key factor for max engine power is the trapped oxygen mass fraction. And this value is helped by having a dense intake charge. The intake charge of an F1 engine is cooled (and thus densified) by the latent heat effect of the fuel evaporation. Cold liquid fuel absorbs more heat during vaporization, so the fuel latent heat effect on intake charge density is increased, thus increasing power somewhat.
It doesn't specifically benefit combustion, but it does improve intake mass flow. But not a whole lot.