What is important to note is that there isn't really a dev environment for the Steam Deck in the same way that there is for consoles. It's just a case of making a PC (or ideally, a Linux version) of your game and then providing a set of suggested settings (inclusive of a controller config) for when the game detects that it's running on the Steam Deck, and that's it:
partner.steamgames.com
partner.steamgames.com
partner.steamgames.com
That's a huge step change from the console development environment where games need to be specifically created for the console. If developers/publishers are complaining about the current predicament regarding xbox versions of their games then this will go a huge way towards solving that - they will no longer need to make a console specific version for "xbox", it will just be a case of making the PC version and then providing suggested settings appropriate for the hardware Microsoft opt to go with.
Even if the developer fails to come up with something appropriate, Microsoft can have a tiny team who can be responsible for sorting that out on their end. Worst comes to worse, the burden falls on the end user (as it does on the Steam Deck).