the distinction would be undetectable to human ears. So why not just tell Leila his other name?
But in that case, Leila would be constantly voicing name all wrong, and Spock would have to listen to it.
Even if the surname of Spock, Amanda and Sarek (and perhaps Sybok) is "Carl" to the human ears and tongues, this doesn't mean our favorite semi-Vulcan would wish to put up with the wrongly shaped vowel, the improperly rolling r, and the l that is 47% too short, not to mention with dropping rather than rising pitch, every time he manages to make Leila happy. It's worse if there are "secret" (ultra- or infrasound etc.) elements there that make all the difference to the Vulcan ear, so that it sounds as if Leila is expressing her admiration of somebody from a different Vulcan family altogether!