Does the par-boiling first then frying work for sweet potatoes as well?
I have done this with boiling and then baking sweet potato fries. They turned out alright, but didn't come out as crispy due to the baking having more moisture to pull out (that's my post-facto hypothesis, anyways). I have to admit I'm not a fan of this method for french-fries either – I find that some restaurants who use it tend to give soggy or mushy fries.

If I recall correctly, it cut the baking time from ~50 minutes to ~25 minutes to get enough of a crust to make them worth eating. For frying, I would expect a similar reduction in cooking time as par boiling cuts for russet potato frying.