I recently did an inner ball joint on my non-assisted ('88) rack after MoT advice on play.
Although play could be felt/heard by shaking the front wheels when lifted off the ground (and visible, when tester did it while I watched the rack) I couldn't feel it on the bench. There's a spring in each inner ball joint that when they're only slightly worn might maintain enough pressure to keep it tight without load, but allow play under the increased weight and leverage of a wheel being swung against the other end of the track rod.
I did have the telltale of the joint flopping under its own weight too.
If you're unsure, you might have to put it back on the car to inspect again. I wouldn't say those joints are fun to service (although maybe I just have the wrong tools...)
Sorry, I meant to say I thought did find a spec, at the time! I *think* the joint is supposed to support 3kg at 30cm without moving... but take that with a heap of salt as I couldn't find a replacement track rod, or achieve that spec with my part-worn one.