@leocg There was a Unity plugin which was EOLed a long time ago, and there is the downloadable Unity WebGL engine which al lot of browser games use, which is started using the 'UnityLoader' javascript.
In that javascript they look for what OS it is running on, and for some reason a programmer apparently assumed MacOS would never move beyond version 10, as the regex looks for "MacOS 10." instead of MacOS 1[/d].", and even that would cause problems when they reach MacOS 20... 😛