Then again, when we first see Legolas and Gimli after Boromir falls, only the elf seems to have actually fought ("all his arrows were spent"), while the dwarf may simply have been hunting (no actual slaying). Legolas might give him credit for slaying too, but Gimli sets the matters right later. It don't think it would have been appropiate for the dwarf to mention at that time that "hey, errr, my feet were to short to catch up with any of the retreating orcs, but I am glad you think of me that way
".