According Gulenko
people pair up: D&H, C & C, N &N
Aligns well with Helen Fisher's personality system.
While the subtype duality is D & N and C & H.
If we assume that N & N happens between introtim and extratim then there exist two subtype match (something like at least 50 % people) which also holds true with C & C introtim and extratim pairings.