Your benchmarks and conclusions don't line up very well.
On Steam Deck you say...
This will make the image quality go down the drain, and you will experience sub-30 FPS frame drops at regular intervals, with some scenes featuring huge enemy hordes beating the hardware to a pulp and dropping the frame rate to below 20 frames per second. And you say... "Is this playable? For me, it isn't, but you do you."
Then on the ROG Ally...
Select the "Manual" power profile and start bumping the TDP value from 16 W upwards until you arrive at a value that gives you playable enough performance. This will prolong battery life to about an hour and a half, perhaps longer if you consider a cinematic frame rate—24 FPS on average—playable.
--- So, Steam deck sub-30 drops and some scenes with huge enemy hordes dropping below 20 fps -- unplayable
--- ROG Ally "average" of 24fps, which essentially guarantees sub 20 fps -- "playable if you consider cinematic frame rate playable"
Seems you're being harsher on the deck, especially since in your benchmarks you show the min frame rate of the deck at 1280x800 as 21.2 fps, and the ROG Ally at 1280x720 at 15.9fps (at 15W) or 21.4fps, same min performance as the deck, but at 25W. And especially since the deck plays 1-1/2 to 2hrs, or nearly 2x as long (these are portables after all) as the 1hr playtime of the ROG Ally at 25W. Of course the OLED Deck would last even longer.