We had an earthquake drill at one place I worked, where there was an outside door less than 20 feet from our desks. Another guy and I agreed, if there was ever an earthquake we were heading out that door and would wait in the middle of the parking lot until it was over and then help dig bodies out of the rubble. Somebody said, "What about falling debris?" It was a freaking 2-story building, but yeah we conceded we'd be taking a risk for a second or two as we sprinted clear - vs expecting our cubicle furniture to keep a collapsing building off us lol.
Having lived through a major earthquake - if it's a brick or concrete tilt-slab building, you are way better off inside the building. The risk isn't so much some random piece of something falling off, it's the entire facade of the building coming down on your head.
I don't think I can outrun concrete that starts falling at the exact moment I start running. What I think is that the odds are low that the timing will be so perfect, and also that the odds of getting crushed under a desk are so much greater running would definitely have given my higher odds of survival in the specific situation I outlined.