Synthetic stocks can warp. Especially the black, oily, plastic ones that most firearms manufacturers use. Those stocks don't adhere well to bedding material also. Getting a good mechanical lock with the bedding is a good way to keep the bedding from shooting loose. I mechanically lock bedding in all rifles I bed, regardless of stock material
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Most folks like just enough clearance between barrel and stock to slide a dollor bill or index card in. That's not much clearance. Depending on barrel weight and stock material, just laying it on a rifle rest can make the stock bend enough to touch the barrel. I always use 1/8" to 3/16" gap in the barrel channel. Builders of competition rifles and sniper rifles aren't worried much about looks andusuallygo with a gap big enough to slide a penny around the barrel channel.