The length of the class once you've removed it does in fact seem to be 1 (ie the space mentioned in the original ticket).
Looking at core, this seems to be being done on purpose in the removeClass function around lines 1297-1282:
var className = (" " + elem.className + " ").replace(rclass, " ");
for ( var c = 0, cl = classNames.length; c < cl; c++ )
className = className.replace(" " + classNames[c] + " ", " ");
Whilst I think a second review to confirm this behavior's need would be useful, I also question what (if any) impact it being in place has on a developer's ability to modify the class at a later stage as it is just afterall a space.
Live test case: http://jsbin.com/obeji4/2/edit
Flagging for second review.