Each rose has its own habits about opening. Many very-double roses will open from tight bud even if the sepals haven't fully separated--but with some roses you need some separation of the petals before you cut.

However, I have no experience with SK. Paul gave this rose a very cool name, and the rose looks gorgeous in pictures.

They were probably still too tight when you cut them to open. I've found on most roses the petals need to have just begun to open on their own before cutting to have them open inside. Just having the sepals down, showing color isn't enough.

I don't know if this works but I've heard a trick exhibitors use to get a too tight bud to open faster for a show is to gently squeeze around the bud to loosen up the petals inside. You might give it a try before you cut next time and see what happens.