Well, those Coopers are generally fine shooting guns...no doubt.
I would say this: what happens when the action screw that threads into the lug is tightened and the lug has clearance on the bottom? The action flexes (common on the Coopers). And the stock flexes. Neither is good.Also, when the action flexes even a bit up front, the bottom of the recoil lug is tipped rearward....so now the back of the lug isn't making good contact.
Keep in mind it's
time consuming to bed a threaded lug receiver correctly. As the Coopers are a semi production gun, I expect there are limits as to what they can spend time on. I've only done one Cooper and bedded the bottom with a short pillar and .040-ish of bedding compound between the pillar and the action...just like this Sako. It removed all the vertical it's owner had struggled with.
Hope this helps.
-Al