I think you're misreading scope ring instructions. The rings should be pushed forward until their crossbolts contact the lugs of the rail, not pulled back. The same thing would be true for KRP's thought experiment: the stock would be pushed forward before tightening. Consider the following diagram:



The acceleration of the red and blue blocks would be tied to the black recoiling mass by the lugs at the top and bottom. The yellow and purple blocks, however, would not be positively restrained and would tend to want to remain still as the black mass recoils, resulting in their relative forward movement. In this diagram, the red block would be the crossbolt of a scope ring and the blue block would be the recoil lug of a stock.

I don't think there's anything necessarily wrong or too detrimental about bedding the front of the lug, so long as it can still be disassembled and reassembled!