Simmering with or without the lid Many Indian recipes give the requirement of simmering the gravy, covered until reduced. I'm wondering if this advice is flawed as one would presume the pan would need to be uncovered in order to reduce the liquid.
It depends on how long the recipe calls for, and how much reduction is required. Most Indian recipes I make don't require much reduction, they are relatively thick to begin with. Lids don't seal perfectly, you will lose moisture even with the lid on. If you have a long, slow cook it may reduce enough for some recipes.