[O] Minibuffer jumping to two lines when agenda displays 3rd level heading

I don't if this is a bug or a feature however to me it's just annoying. I've recently noticed that when moving up and down the agenda some entries will cause the minibuffer to expand to two lines while others make it shrink back to one. From bouncing around a bit, the one thing in common I

Re: [O] Minibuffer jumping to two lines when agenda displays 3rd level heading

FWIW, the minibuffer behavior does not occur in NTEmacs. GNU Emacs 24.2.50.1 (i386-mingw-nt5.1.2600) of 2012-08-24 on YAMALOK