Stihl isn't in the business of custom chain loops. I wouldn't expect them to sell you a custom chain...that doesn't make business sense for them.
My stihl dealer will make me Stihl chain in any driver count I want. I've gotten Stihl brand chain there for my Echo saw on several occasions which is an odd driver count according to Stihl. So it's not Stihl, it's your Stihl dealer that's the problem.
That's the only sensible reason I could figure. … but Thanks none the less! … Stihl's Chain, good stuff.
The only Stihl dealer around that is still a traditional saw dealer and not selling saws on the side (which is quite a drive from me) will make loops in any DL count I want.