I noticed this too and did some troubleshooting. It appears that in UE4, impart velocity is based on both implicit and explicit velocity. In other words, changing an objects transform gave it velocity, just like directly setting it’s velocity.
In UE5, it appears to use only explicit velocity currently. Changing an objects transform does not implicitly generate velocity, thus there is no base velocity to impart. If you set up velocity explicitly, it is imparted as expected. I’m not sure if this is a bug or intended.