Ferrari appear to recommend different change intervals for different models. This may just reflect a better quality of part is used for later cars, as Stradale's servicing says 30,000km or 3 years, but my Mondial 3.2 (1987) calls for :
"Replace timing belts every 35,000 - 45,000 km, or 24 months maximum"
I agree that hardly anyone will every hit the mileage limit & will instead be faced with changing the belts every 2 / 3 years. I'd go with what your manual says, as it is probably based on the life expectancy of belts made for the funky GT4. Maybe 360s, etc use a different tooth profile with a lower belt tension - I dunno.