And more importantly, all the money goes to Microsoft.

I would bet that the Xbox Accessibility controller will never be profitable for Microsoft

It doesn't have to be profitable for them. It can just exist, be the only option, and prevent others from making a competitive or superior product, forcing others out of the business.

It would be a shame if someone with a physical disability needed to find a different accessible controller for each platform they play on because each one only supports first-party controllers though.

I don't have a disability serious enough to need adaptive controllers like this, but I do have RSI, and when I find peripherals that I can use with minimal pain I stick to them. I have to imagine many with more serious disabilities would feel similarly.