It's not the accessibility tools that do that, it's the default browser behaviour.
We could however introduce another attribute that has the correct behavior, deprecate `disabled`, and throw warnings during ARIA validation/linting for pages that continue to use it. Call it `blocked` or `unsusable` or have if you want to be fancy, make a `status` or something with attribute with multiple values that it accepts. Whatever seems most reasonable.
But my point is we're not trapped in the world of developers needing to poorly replicate browser functionality for every single form they make; we could still have an attribute that makes it easy for developers to by-default program forms with the correct behavior.
In Javascript, adding `let` and `const` didn't require us to get rid of `var`. We didn't have to change `var` behavior to make `let` throw errors on redeclarations. There are options here for providing tools within browsers that work correctly.
Also there's standardization and coordination between browsers, but if there is a genuine need for something they tend to find a way.
The browser's focus has to be taken as the gospel truth, because that is the only thing that all these different assistance tools can agree on. There is no standard otherwise. If you want to be a smartass and develop a speech-to-text tool that does it's own focus management separate from the browser's, well now people who need custom input solution can't use your tool, because what they are typing into (browser's focus) is different from what your tool is focusing on.