Why …? My --> “guess” <-- is that Magpul probably offered ‘em a really honkin’ deal on a truck load of X-22 stocks. In a cruise through the SS Match barrel Q&A section you’ll find that Kidd still recommends fully floating the barrel for best harmonics, which translates into greater accuracy potential. Titan stocks, with or without their version of the Kidd receiver rear anchor, allow you to adjust out any clearance betwixt their stock and trigger housing’s backside, or with their Kidd rear anchor, bolt down the receiver’s backside, either way allowing for a full float of the barrel all the while preventing the barreled action from teeter tottering within the stock, pivoting overtop the original design’s single action screw. The X-22 stock design relies on a still better than nutin, barrel proper upper thing-a-ma-jig located somewhere within the barrel channel.