My first car, a 1950 Merc, owned from 1955 to 1958. I didn't experience 'bump steer' either because I didn't know better, because it hadn't been invented yet, or didn't happen because the front end was new/tight. Or maybe Ralf Nader wasn't around then.
Fast forward 60 years to my present 1950 Mercury on which I've spend absurd money on the steering. Spending a few hundos more on the steering would be beer money, I've googled for an answer and posed your question to alignment guys and an early GM steering engineer the later who I put most faith in. Virtually the same answer, the supposed bump steer is mostly imagined unless you have a loose front end and drive like a bump steer kind of guy.
Theoretically, the steering link which connects right and left wheels and the pitman, should always maintain the same horizontal plane. This even though the car is in a turn and one wheel goes up (the bump) and the other goes down (think pothole). This may cause one wheel to turn more than than the other.
In real life the error is generally small enough to be ignored. However loose king pins and bushings can cause real bump steer. While I am told the error causing evil bump steer was reduced in later years, this 'upgrade' does little to reduce it significantly. Take the picture under your car as I did, and figure the dimensions involved. So, while I have the money, time, and energy to install the 'upgrade', I am ignoring purchase of the above steering improvement gizmo.
Sorry but that's the reason I'm not the user who can vouch for the product.