Yes, we know that. That's why the collapses took about 15 seconds (not counting the core remnants, which failed ~20 seconds after) rather than about 9 seconds.
What you're doing, however, is using this analogy to claim there's no way "gravity alone could have made the buildings down, particularly as quickly as they did." This is wrong.
What you're doing we refer to around here as the Unevaluated Inequality Fallacy. In this case, Quantity A is how fast your giant baseball in water would take to fall. Quantity B is how fast the Towers would collapse with gravity alone as the responsible agent. You haven't calculated A, you don't know B, yet you insist that you do know the relationship between them.
Balderdash. Once again, there are peer-reviewed papers on the collapse timing, multiple ones from independent sources, and they all agree with the actual collapse times. You're simply ignorant of this science. And your weak analogy is hardly sufficient to challenge them.