When you fire the rifle the stock "balloons out" in the magazine area, which is why cross bolts are used to stop the stock splitting. When the stock balloons out then the stock in that section becomes shorter than the action. Thus the tang hits the stock material. Also the reason that there needs to be clearance around the action screws.

The mistake made by many people is to put one warp of very thin tape around the tang because they think the problem is caused by the action setting back a thou or two in the recoil lug area and thus very minimul clearance around the tang should be OK. When I bed rifles like Howa/Vanguard that also have a tang that will rest against the stock, I use 3 layers of masking tape around the tang and just folder over the bottom of the tang by a small amount. That way nothing has to be ground out after the bedding is done.