Leadsled, the designated PIC in NZ cannot always use their PIC hours towards an ATPL:
from part 61 "A pilot who is designated as pilot-in-command for the purpose of rule 135.505(b)(3) to supervise a pilot undergoing consolidation of operating experience may not credit the pilot-in-command flight time towards the flight time experience requirements for an airline transport pilot licence if the supervision is carried out in a single-pilot aircraft under rule 135.505(c)(2)."
(135.505 deals with requirements for ICUS)
But also one paragraph above it also states this:
"A pilot may not credit flight time recorded as pilot-in-command under supervision (PIC/US) towards the flight time experience requirements for an airline transport pilot licence"
So together, two pilots, one as PIC and one as ICUS, neither benefit much! (only in terms of gaining a NZ ATPL) Although hands on skill and experience still is gained!