Unable to open non-searchable dropdowns while Windows Narrator is active.

During a review of our product using a screen reader, namely Windows Narrator, I found that only some of our dropdowns would open.
After some debugging it seems the dropdowns only work if isSearchable={true}. This makes dropdowns unusable for users using Windows Narrator, where the dropdown is not searchable. It seems to be because of the aria-readonly="true" that is added to the input.
Example: https://codesandbox.io/s/codesandboxer-example-forked-v8b000?from-embed=&file=/example.tsx

I have not been able to find a working solution, except enabling isSearchable.

Additionally I could mention that it seems screen readers announce 'Press Down to open the menu' when Space is actually the working key to expand the dropdown.

Is this something that's already known?

Start with the linked CodeSandbox example.tsx and reproduce the non-searchable dropdown with Windows Narrator. Inspect how aria-readonly="true" affects opening and the announced keyboard instruction; done means non-searchable dropdowns open with Narrator and the announcement reflects the working key.