Where I differ is with your (admittedly contrived) example. I've interviewed dozens (hundreds?) of people over the years, and I can't say I've seen any correlation between passion and professionalism/competence/longevity.
I think "Hiring for passion" is the new "Nobody ever got fired for buying IBM". It's the CYA response. We have no clue if a hire is going to work out, but if they spend their weekends writing C# for fun, and they don't work out at our company, we can at least tell our bosses "They came across as so passionate during the interview -- we couldn't have known they would turn out to be a bad hire!"