There's not enough data to support this claim. At present the budgets spent on policing space for foreign objects is puny, and currently less than 5% of the night sky is being policed or analyzed. Asteroids can come from a bazillion different trajectories up down left right.. all in 3d space... it's not like looking left/right and left again crossing the street.

It's very possibly an asteroid could strike us and we wouldn't even be aware of it till after the fact, or at the very least till a week or two before it strikes... if it's in one of our blind spots (i.e. the other 95% of the sky)

It is not yet possible to know when the next one is going to show up. We are only currently aware of a bunch of rocks that most likely wont hit us.

That's 100% of the point.

If other planets/moons/whatever haven't been colonized by the time humanity gets empirical data for that hypothesis, a lot of people are going to wish they'd put that a little higher on the list.