Programming

This is a ridiculous definition of “real-time”. To accomplish this you’d need to subvert the kernal’s scheduler (...)

You missed the whole point of the article.

It makes no sense to read the article and arrive at the conclusion that "I need to subvert the Kernel's scheduler". The whole point of the real-time analogy is that handlers have a hard constraint on the time budget allocated to execute each handler. If your handler is within budget them it's perfectly reasonable to run on the UI thread. If your handler exceeds the budget then user experience starts to suffer, and you need to rework your implementation to run stuff async.

Keep in mind that each mouse click/hover/move/sneeze triggers a handler on GUI applications. Clicking on a button can trigger small, instant changes like updating UI, or can trigger expensive operations like running an expensive task. Some handlers start off as doing small UI updates but end up doing more and more stuff that ultimately start to become noticeable.