That's not the same thing. For example let's say I want to run the Game on an SBC. How do I do that reliability without a Linux port?
Depends heavily on the SBC. If it has an x64 processor, then Linux + Proton would probably work fine. If it has an ARM chip, like a Raspberry Pi, you'd be lost either way. ARM-based SBCs don't run using "normal" Linux. They need special ARM versions of Linux, which themselves need ARM versions of all the software they run. You'd be asking the devs not only for a Linux port, but different Linux builds for different chip architectures. That, or you would need an x86 emulator, like Box86.
Besides, OP was asking about Linux compatibility because of their Steam Deck. That's very much Proton territory.
The point I was trying to make is running things through Wine or Proton is not a one shoe fit all scenario. Also it's annoying when people say "Just run it through Proton or Wine" because running any game through a compatibility layer always takes a hit it performance. Also you can run into functionality issues with some games. This is why people ask for Linux ports because it fixes most of these issues and also gives you more freedom and options when playing a game.
Alright. The only thing I'd say about this is what most people have said already. Maintaining multiple ports bears real, non-trivial cost, varied by the libraries used, and it'll be a long time before the Linux marketshare is large enough justify the investment to most dev teams (in spite of being disproportionately vocal). Imperfect as they are, P&W are needed to bump those numbers.
It seems like asking for Linux ports is kinda your thing, so I'll leave you to it.