Not believing in free will does not inevitably lead to a nihilistic funk.

Funks are often caused by an abrupt shift in worldview without a corresponding set of tools for integrating that worldview into the rest of your life.

Calvinists and Sunni Muslims don't believe in free will. Neither one as a class could be said to be in a nihilistic funk.

Substitute "free will" for "God", and it basically seems like a restatement of Pascal's Wager, along with the prevailing (and untrue) belief that atheists (or, in this case, those who reject free will) are incapable of morality or of finding meaning in life.

It has superficial similarities to Pascal's wager, but it is not the same.