Well. It doesn't say in any docs or specs, but for what it's worth, Valve's hardware has always been open like that. You're free to install windows on your steam deck, for example.
Valve sponsored asahi linux which was a herculean exercise in running another OS on locked down hardware. They've also sponsored wine and fex. It would be a sudden, steep, and unexpected departure for them to go from being leaders in cross platform OS/hardware support to locking down their own hardware platform. It's just not in their nature. They know their nature is good and they know we know it. That's called trust.