Let’s just leave the post credit scene up to interpretation.

So what If it has Marcos ghost in the background or if it doesn’t make sense, a scene can be funny and impactful at the same time. AOT isn’t about realism and people can make their own theories. This fandom gets to argumentative over small things in this anime. Why can’t we give our takes without trying to correct them. and If you don’t like the scene…well then don’t watch it.