I should add that osmi areas picked up the invalid multipolygon
https://tools.geofabrik.de/osmi/?view=areas&lon=152.95314&lat=-27.25959&zoom=19

If you really want to use a multipolygon for this you could have the two building parts in the multipolygon as role outer and remove the central part from the multipolygon and tag it as a roof. 
You would then have a valid mp as the 2 buildings do not touch and the roof would render when tagged separately.