Works well enough for me. Some cultures, I believe, don't even have family names, correct? So, it's entirely possible that "Spock" is his only name, everything else could just be a Terran interpretation of the Vulcan language.
Ideally, all Sikhs are named Singh and Kaur. Surakism seems at least as radical a break with the Vulcan past.
Singh and Kaur are supposed to be the universal male and female surnames
for Sikhs, not their only names. Sikhs always have first names, even when they don't use the Singh or Kaur surnames.
In a large society, especially a planetwide one with six billion individuals to distinguish, it would just be irrational to require everyone to go by only a single name, especially when most such names are only five letters long and begin with S and/or end in K. There's no possible way to get six billion distinct names out of that. Having family names is only logical -- especially given the evident importance Vulcans ascribe to their family ties.