Sealed bearing axle move left to right versus up and down when loose. To check for play in sealed bearing hub you have to remove the wheel from the bike and push on the axle left to right versus wiggling it up and down. Sealed hubs dont have 'cones' but for the purposes of this discussion you'd loosen the 'cones so there's some left to right movement when the wheels out of the bike which should disappear when the skewers clamped.

Unfortunately its very difficult to tell if your adjustment out of the bike is too loose once the skewer is clamped. I usually adjust these types of hubs so the heavy spot oscillates a few times at the bottom