Really?
I'd guess that the orbits can't be calculated that far into the future for such small objects due to gravitational influences of large (planetary) masses.
I don’t think it’s a technical limit, it’s just that they don’t want to have an official prediction of some catastrophe centuries into the future. The small planet center, the people who track asteroids, are the exact opposite of global warming alarmists. They take their job seriously, and attempt to downplay any alarmism, and tamp down lurid press reports. I worked as a contractor a MIT/Lincoln Lab, and worked with the woman who was project manager of the original Lincoln effort to find earth crossing asteroids. She’s the only person I know who has an asteroid named after her by the IAU. They used a one-meter telescope in Arizona (some amateurs have better telescopes) and increased the number of known earth crossing objects by a factor of about ten in two years, under an Air Force contract. Lincoln has since left the business, leaving it to others, now that they demonstrated proof of principle.
The three-body problem cannot be solved exactly (unlike the two-body problem). 100 years of perturbations would result in statistical probabilities as meaningful as the weatherman predicting next September’s weather.