Unless this article concerns just US and other English speaking countries, the first problem with "accessibility" is that of language.
A lot of Linux software isn't completely translated. Even the UI often has things that show up in English, and typically the supporting documentation, help etc, is completely untranslated.
Linux may have a bit wider language support, but it's very shallow. E.g. in Windows, any languages it supports, it supports fully. This rarely extends to third party SW though, so there Linux may have some advantage.