2023 Crosstrek Auto shutoff

Whats the idea of turning the engine off when u sit at a light more than a 
few minutes? Saves gas?

Tried to disable it, there is an (A) on the display and a line gets drawn 
thru it so I guess that means its disabled, but it still seems to turn off, 
unless its a stall problem but it starts up soon as you take the foot off 
the brake.