Possible bug in 'more-rooms' module?

I attach a simple xml file that demonstrates what I think is a bug in
'more-rooms' module.

It appears that the restriction 'teacher-also' doesn't check that the teacher
is allowed to teach this subject - although the teacher does have to be
defined to teach something.

This may not be a bug but if not, it is (a) inconstent with checking for the
main teacher and (b) makes it harder to spot mis-allocated teachers.
 
Kind Regards

Nick Robinson