Collar Conditioning Question

I'm not to far away from starting the collar conditioning process with my dog. I'm following Fowl Dawgs and when he does collar conditioning he gives the command then gives a nick the gives the command again. I have only done collar conditioning one other time and I did it following the book by Tom Dokken and he teaches collar conditioning by saying the command then giving a nick while also giving pressure from the collar. What are the reasons for giving the command twice with a nick in between rather than just once? It seems like the way Tom Dokken does it follows more with the way formal on is taught. I'm just trying to figure out which is the best way to do collar conditioning. Thanks