I think in this case it was right to post it to Bug because the cause was not known at first. Then it should have been merged into the theme component topic. Until then I think it could have stayed in Bug, perhaps with a tag indicating that a component was the culprit?
I’m not fond of the General category which has become a catchall for all manner of topics. I can see a world where people post to General because they don’t know where it belongs but moderators move those posts to the appropriate place if it exists already or perhaps create a new category if enough similar topics are landing in General.
Sam, feel free to use the flag too if you are feeling lazy in cases like these. Then moderators can take care of it.