"True" and "out of dish" or not centered are two different things. A wheel can be perfectly true, yet not have the rim centered between the locknuts. More common on derailer gear wheels, but can happen to any wheel. Try flipping it over in the frame. If flipping the wheel makes the tighter gap change side, then the wheel isn't dished right.
Or spacers/washers haven't gone on right by the axle nuts.
It's an easy enough fix. but re-dishing needs some skill or self-control to avoid messing things up more.