It's not an Emacs bug. Your regular expression whittles down to:

(defvar hang-re "^\\*+ *Mawile\\(?:[ ]+\\)+stuff\\(?:[ ]+\\)*$")

or even

(defvar hang-re "\\(?:[ ]+\\)+s")

That expression matches the string of spaces separating the first
Mawhile headline from its tags in many many different ways, and is one
of the type of regular expressions warned about in the (Emacs Lisp
Reference) manual. We shouldn't be generating it, and it is a bug, but
it is in Org, not Emacs.