He specifically cited bad battery life on the ROG Ally and Lenovo Go, saying that getting only one hour of battery life isn’t enough. The Steam Deck (especially the OLED model) does a lot better battery wise, but improving power efficiency should really help with any games that are maxing out the Deck’s power.
the idea of it improving battery is that generating frames is less performance intensive than running a certain framerate (e.g 60 fps capped game with frame gen at double the framerate consumes less power than running the same game at 120 fps). though its slightly less practical because frame generation only makes sense when the base framerate is high enough (ideally above 60) to avoid a lot of screen artifacting. So in practical use, this only makes sense to “save battery” in the context that you have a 120hz+ screen and choose to cap framerate to 60-75fps.
If one is serious about minmaxing battery to performance in a realistic value, people should have the screen cap at 40 hz, as it has half of the input latency between 30 and 60 fps, but only requires 10 more fps than 30 which is a very realistic performance target for maintaining a minimum on handheld.