Mine has a more shallow angle and I stopped at the root of the tooth
(only the flat wide part was left unsanded).
You can see from the rough grind marks that your belt wasn't very tight when you ground it, and it wasn't moving very fast either.
Using a sanding disc on the same grinder can give a smoother surface.
Still, the free load and unload bevel action does stop the flat side squeak, now don't it .....
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Here is a pic of an old, many miles side ground belt, showing all the polish that takes place as the miles roll past.
It also shows the Bando belt's original construction style, the cloth supported tooth surface, the raw plastic inner core of the teeth (the part that makes the squeak) and the cord and fabric nature of the thin flat section that carries the load.
Sero, your belt looks a bit like a toothed rubber belt ???