FWIW:
Many belt drive rear pulleys have one cast shoulder, and one pressed or screwed on shoulder. The cast one is always on the outside of the pulley.
If a wheel/belt was set up to load the inner ring of the pulley, it would be pushing against a lightly pressed on piece of sheet metal. Not good.
The way I do belt adjustment:
Jack under the bike. Rear wheel free to spin.
Get the slack pretty close.
Play with the adjusters so that the belt is fairly centered.
Turn the adjusters so that as the wheel is rotated, the belt slowly migrates to the outer (cast in) shoulder. Not so much that it is scraping against the edge.
Double check the belt slack.
Torque the axle nut.
Recheck the slack.
PS:
It's is usually easier to keep the adjustment if you have the axle nut on the right side of the bike, not the left.
(ask me why
)