I've heard of it. It's really messy stuff - imagine tooth paste made of dirt and tar. So I'd suggest placing newspapaer over your unit and hearth when using it, and when you put it on the flue, add it to the male parts so any extra goops inside the pipe instead of all over the outside.
Yeah sure - and I agree, its not a common type of sealant so they should have included it or spec'd a few others. I'd use RTV silicone on the outer pipe just to be sure it's sealed. The stove cement will harden and become brittle since it's so thin just like concrete would and after the pipe expands and contracts for several cycles the cement will break lose in places. So I'd use RTV on the outer pipe to be sure the pipe never leaks inside the house.
Don't just take my word for it though, call Jotuls customer service and ask them what else you can use. Sorry have to say that for insurance purposes....... hh:
Sealers on a gas unit??? Are these mfgs in the dark ages? Snap the pipe on and go, that's how all the stuff we use works. Furnace/Stove cement is worthless, I have serviced many fireplaces with that crap on the first joint, 90% of it is laying on the burner pan after it gets brittle and falls off.
If you can't find Mill-Pac, Rutland sells a product called Seal It Right which is about the same thing (withstands 800ºF temps and remains flexible). I am surprised no one in your area stocks Mill-Pac. Many appliance manufacturers have it in their installation instructions.