I've hatched and raised four roosters total, and those with walnut and pea combs were all substantially larger and more red by 16 weeks. They were clearly standing out from the pullets by 12-14 weeks. I don't think there are any super clear images of the hackle feathers, but the saddle feathers are clearly rounded and look very much like a pullet to me.I'm still not sold on cockerel, but I've not raised brahmas before. My EE mix roosters with pea combs had significantly more prominent combs and wattles at 16 weeks then I'm seeing here.
ETA: I should say significantly more at 14 weeks, as that's when they were culled.