Yes this seems to be the best indicator yet that Ive seen for males vs females in all the breeds I have. Now its hard to compare breed vs breed but within the breed this is true. Another factor to consider is that hybrid vigor may throw off the normal feathering rates and produce a bit of confusion.Tail feathers grow slower on males .
Typically day old wing sexing works on a number of breeds as the wing feathering is typically different from male to female but Ive read so many variations that you would need to know which pattern determines which for your breed and its only viable for the first day or two of wing feather growth which in hybrids can be very fast. If you are looking for sexing traits then you will simply have to keep track of the indicators on your hatches to come up with something that works.