Bearing play may be more noticeable in the vertical because there is less flex in the suspension mounts than in the steering linkage. Still, my guess would be strut wear. How much is acceptable would be tough to gauge based on a print description.

Note, though, that loading with wheels on the ground is different from your tests. I would also check this way. You may find less strut movement with the strut in a more normal range - or more.

Steve