If I were to speculate, they are waiting for the NVK (Open source NVIDIA driver) to be more mature. So, they wouldn’t have to release two versions and wouldn’t depend on NVIDIA to update their driver to work with software the Steam Deck uses. I.E. Steam Deck uses gamescope for everything outside of Desktop mode. NVIDIA’s driver didn’t work with it until 2 months after the Steam Deck release. Even though it had existed for years prior.