I don't know, but I do know I would rather fix a race condition on a multithreaded application than figure out how flexbox works or even understand all the different parts of the DOM.
You can fix race conditions on single threaded JavaScript code now we have async (and promises): it scares me how little this is recognised as a downside and in my experience few people are good at recognising or writing code that avoids race conditions (I have seen competent programmers in denial about the risks).
Before async I found race conditions in popular (and well written) JavaScript code that used setTimeout().
Personally I think anyone that enjoys chasing race conditions is mad: I loath reproducing transient errors. I have mostly tried hard to avoid async code in my own JavaScript, but sometimes it is forced upon me :-(