Indie gamers won't come to Stadia anyway.
My guess for this is that given Terraria's large fanbase and high profile, Google probably handed them an advance for this and promised some promotion once the title launched on Stadia. Stadia also potentially provides access to users who can't play it on PC (it has a client for phones and some TVs, etc)
OT - where does your username come from? I'm sure it's not, but for a Brit to read it, it stirs thoughts of a terribly un-PC origin! :)
It wasn't until a few years ago that I stumbled upon an Urban Dictionary entry for it. That was so disappointing because I always thought I was so creative coming up with that unique and interesting-sounding name...like Tolkien!
I'm definitely not important enough for anyone to bother cancelling me over it (especially considering how mild and obscure it is), but I've stopped using it just in case. I still have a lot of old accounts lingering around that use it though.