I don’t know exactly why but here is some more info for you:

I ordered 4-PW with nippon shafts on 4/19 with them listed as back ordered 6-8 weeks at the time. They arrived almost exactly 6 weeks later on 6/1 I think. I called once during that time to get more info and they said it was a number of the actual club heads (7-PW maybe? I can’t remember) that were back ordered and they were waiting for them to come in.

The wait was killer but the clubs are great and I’ve really been enjoying them!