Sorry, even if you assume (generously) that it only takes 5 minutes to play a par 3 hole compared to a 4.5 hour round (again, generously slow), then a par 3 course is only 1/3 of the time AT BEST.
As for the 90% of the fun, well... I tend to disagree. It's not that I just like cracking the driver, but the diversity of lies that one gets to hit full shots from, not to mention the increased strategic options afforded from 2+ shot holes are things that I miss. Short game is a huge part of the game, and green complexes are a vital part of course design, but they aren't everything.
So, is Coore right? Well, in my opinion no. But I do believe he is being hyperbolic to make a point. And that point is probably that par 3 courses provide greater fun in relation to size, time, and cost of a regulation course.