

No, because not every game should be a controller game.
Controller support is already a filter available within steam. It should not be the primary and only way to use a gabecube. It is not a handheld device or solely a HTPC class device, it’s a full blown computer.

What part of the steam machine page shows a controller as the default mode? They have three videos of people using it. A single one has controllers… the other two are as desktops.
The thing is designed to be compatible with steam’s controller, but it’s not just for controllers. It is sold without the controller, but you can buy a bundle with a controller. The wording on the page carefully notes that you can “use your steam controller without it’s puck” because it has a receiver inside of it, that’s it.
The deck is a default controller device because it clearly is just a big controller with a screen. The gabecube is literally a ultra small form factor PC, intended to be plugged into a display, and bring your own peripherals. There’s no default peripheral.
I think something like this https://store.steampowered.com/app/1818940/Typing_Land/ should be perfectly verified on the cube. By making controllers the “default” that title could never be verified, it would always have a nasty yellow mark despite running perfectly fine.