>Based on the change in the binary orbit period^2 , we find an instantaneous reduction in Dimorphos’s along-track orbital velocity component of 2.70 ± 0.10 mm s^–1

I should have read the article more closely. I thought they meant the angle changed when what really happened is the speed reduction increased the orbital period by 33 minutes.

After giving some consideration as to why they'd write it like that, it makes sense. Changing the orbital period by an amount of time may be enough for another orbiting body to get out of the way.

My bias got in the way of this one, thanks for the correction.