What is this section for? How does it interface with the neutral being a current carrying conductor when more than 3 are in a raceway. adjustment factors apply?
My answer: first you calculate the load, then you pick a conductor that has sufficient ampacity for that load. Third (not related to your question) you pick an OCPD that will protect that conductor. In your case, you use 220.61 to calculate the load that the neutral wire will see. Then you use the ampacity rules in 310.15(B)(16) to figure out what size wire to use. That step is where you deal with more than 3 CCCs in a conduit, or with higher than 30C ambient temperatures.