Polishing is only necessary if needed, which usually advised by mechanic. Some prefer and some dont to save time, so its quite grey area for end user to understand which decision is good and bad and why.
Just for peace of mind: Drive to shj industrial area behind shj city center, and get the brake drum polishing done in 200 dhs for all 4. Keep 2-3 hrs in hand. Go and seek any mechanic and ask him to remove the brake drum and sent to Lathe/turning (AKA Makrata in mechanic language). Pay 100 for labor to mechanic to open and fit and max 200 for lathe for polishing.