the current aero load is as useful for a driver as the current grip level. zero. It changes so fast at braking, turning in, etc etc, that there is no time to react on some kind of gauge or buzz. Racing a car on edge is about remembering and predicting the grip levels (and aero levels) and for the aliens on the grid, that special feeling that makes them almost predict the tiny amounts of variation.
They do a couple of laps, go into the pit and they study the laps with their engineer. "in turn two it looks like the slip angle isn't yet optimal, the aero load indicates that you could gain there about 5 kp/h on the apex". Driver gets in the car and does the apex with 254 instead of 249.