From a performance engineer's perspective, the captain is quite correct.
The certification landing distance is measured from a height of 50 ft above the runway. Perhaps that is not so relevant because the procedure for determining the certification landing distance is not representative of normal landings in service.
When landing on a 'shortish' runway the threshold should be crossed at a height of between 30 and 50 feet. Ideally the Papi should be set to provide a threshold crossing height of 50 ft. On a runway with a 'fairly steep upslope' it should also be set at lower approach path angle to maintain (if possible) the same screenheight-flare-touchdown geometry and optical perception of the runway as on a level runway.
Just my opinion.