I understand your confusion. I experienced this too. I am guessing--as I am no EXPERT on cochins--It is a juvenile roo. Cochins do develop hackles, but very close to maturing. I would say this one is close because I see some faint signs of hackles lengthening. Also, it takes a long time for them to develop the rooster tail and even then, it is not really visible.
None of my cochins ever had wattles and a comb like that. Did you check the legs for a spurr bump?
If I am correct, he should be jumping hens at this age. Cochins will jump any hen they can and they are very active at this. Full of energy; those little buggers.