in the end I'm clueless about the EDT, apart having heard of it, so details like the ones from David Byron are a bit obscure to me.
if the certif can be obtain without taking specific care of the EDT, all the better then. I'm a bit surprised though because not taking care of the EDT is normally a recipe for disaster in bigger applications (once again, from what I read), from slow perf to randow multithreading issues.
AFAIK, the substance L&F (https://substance.dev.java.net/) even takes extra steps to make sure the user doesn't do too much crap. If I was to properly implement the EDT, I would dig into their recommendations.
I had a look into my GUI-code, no references at all to SwingUtilities. Like I already said before: the GUI is very simple and limited, so it makes no sense to compare with fully-fledged professional desktop applications.