Well, the entry for kama in the does not say that only five of the six senses are meant. Sense desire can operate across all six senses, based on contact, feeling, and craving, so to limit this word to encompass only five of the six senses seems artificial. So, I was hoping to see your reasoning with respect to a five-sense understanding of this term.
The five cords of sensual pleasure (kamaguna) seem to set the mentality sphere aside, so is there some other sort of desire and craving which operates in that sphere? For example, kamacchanda is a mental phenomenon, as I understand it, and there is the case of kam'asava, a mental influx. So while kamaguna is the five physical senses, kama itself as a term doesn't appear to me to be limited to 5/6.