Vlad after a few minutes and refreshes it stopped defaulting to 360p. Changing the user agent to chrome on a fresh installation also makes it default to HD/4K right away. Not sure if this issue was just me, but if anyone else ever experienced this, let us know.
I've heard that this is also an issue in Safari, so it might be a WebKit/Safari User Agent bug in YouTube. I guess the only way to reproduce this would be to try on a fresh install (or maybe clear cookies on YouTube.com? I haven't tested that method)