Well, no, because some have impacted Earth before. But if we limit ourselves to large bodies, yes. The current record holder is 99942 Apophis, which briefly had an estimated probability of 2.7% of an impact in 2029 (which has since been eliminated as a possibility). Apophis and ZTm0038 are around the same size.
If ZTm0038 does indeed have a 3% chance of impact, it would, like Apophis, land as a 4 on the Torino scale, tying the record for the most threatening asteroid in history. Unlike Apophis, however, the impact has a lead time of hours, not decades. Efforts might have been made to deflect Apophis; no such effort could realistically be made for ZTm0038.
It's worth noting that NASA's Scout page (https://cneos.jpl.nasa.gov/scout/#/object/ZTm0038) for ZTm0038 has a much higher probability of impact: of their 1000 sampled orbital solutions, 160 of them impact Earth. A 16% chance of impact for a 400m asteroid would put ZTm0038 on the border of a Torino 5, and would make it by far the most threatening asteroid ever discovered.
That said, note that the prior here has to be that an impact of such a size is very unlikely. Such impacts are exceedingly rare. The Tunguska event, for example, was an asteroid 1/8 the diameter (so 1/8^3 = 512 times smaller in volume) as ZTm0038, and it was by far the largest impact in recorded history. Since impacts roughly follow a power law, the much larger putative impact of ZTm0038 would be proportionately rarer, the sort of thing you'd see every hundred thousand years or so.
If ZTm0038 does indeed have a 3% chance of impact, it would, like Apophis, land as a 4 on the Torino scale, tying the record for the most threatening asteroid in history. Unlike Apophis, however, the impact has a lead time of hours, not decades. Efforts might have been made to deflect Apophis; no such effort could realistically be made for ZTm0038.
It's worth noting that NASA's Scout page (https://cneos.jpl.nasa.gov/scout/#/object/ZTm0038) for ZTm0038 has a much higher probability of impact: of their 1000 sampled orbital solutions, 160 of them impact Earth. A 16% chance of impact for a 400m asteroid would put ZTm0038 on the border of a Torino 5, and would make it by far the most threatening asteroid ever discovered.
That said, note that the prior here has to be that an impact of such a size is very unlikely. Such impacts are exceedingly rare. The Tunguska event, for example, was an asteroid 1/8 the diameter (so 1/8^3 = 512 times smaller in volume) as ZTm0038, and it was by far the largest impact in recorded history. Since impacts roughly follow a power law, the much larger putative impact of ZTm0038 would be proportionately rarer, the sort of thing you'd see every hundred thousand years or so.