Actually Luke you did see some LH 744 in combi configuration!
Out of the 30 in the fleet 7 are combi.
However all 7 have been in a full pax configuration since a few years now and have had the doors deactivated and the opening mechanisms removed. (which of course can be reversed.
It is rumored that these 7 will be the ones to leave the fleet in the near future as they can easily be converted to freighters.