The article warns that passkeys could be used, assuming they become the only form of logging into platforms, to prevent someone using the wrong operating system to log into those platforms.

Being prevented from using certain applications because you use the wrong OS is nothing new, but there is, from everything i have seen, always a reason to block it, they dont do it for someone elses benefit. A lot of banking apps cannot be used on many android roms; without microg or gapps many android apps wont work (some wont work even with microg); games sometimes use kernel-level anticheat that forces players to use windows; people solved this issue by just not using those apps

Why would a significant portion of used websites/applications that require accounts stop allowing passwords or authenticator apps, relying on this open standard, force certain options to be used for the standard and ensure that the user isnt on an operating system they have no reason to care about. There are already methods to prevent people from using a certain OS, they could just not rely on an open standard