The Vade Mecum says it’s covered by the patent on lens design Voi013, which looks just like Figure 6.11 in Kingslake—a symmetrical 3+3 like a Dagor, but with a different arrangement of elements.
Yes, they are but not the same, I have seen Dagors of all sizes, Collinears are much rare in big sizes and you could see Dagors in many cameras but Collinear normally in Voigtlander ones.