The "work is their passion so it's not work" contrarian-ism is certainly not uncommon. But the argument against 80 hours is generally stress-induced health and productivity related. Given, if a person "loves what they do" then the stress part is probably lower, reducing the negative effects of the first.
But the other argument is that, after so many hours, returns on effort are reduced, and I don't see a good argument for this being not true whether a person is in love with their vocation.
I would posit that a likely scenario, is that the 80-hour-a-weeker's passion for their work their concern for efficiency. They don't get as much done per hour, but they don't care as much because they love the parts even where they are just plodding along.