I most certainly do not consider 2-4" groups as being acceptable hunting accuracy. My rifles have unerringly produced 1" - 1 1/2" 3 shot groups @ 100 yds. I have targets from my current pre '64 .30-06 to back up this assertion.
Its all about standards. Some/most guys live with that kind of accuracy. Others want their rifles to be more consistent shooting and not have to worry about things changing year after year. Glass bedding has many positives. I don't condone glass bedding a collectible all original pre 64 rifle, but if it has had a recoil pad installed, all bets are off and it's fair game. Another thing glass bedding does is protect the stock from cracking out under recoil. I've seen a few pre 64 338's with cracked stocks. The 375's were prone to cracking, that's why the last couple years the factory installed through bolts in the stocks. Keep in mind, accuracy requirements are to be left up to the individual who owns the rifle. Mine have shot very well after a proper glass bedding job. I've tricked out a few in my day and they have all shot lights out.
Your "1 1/2" 3 shot group requirement is fine for you. As is the 1/2" requirement I have. Different strokes.. Sub moa 5 shot groups work as well. Even with crappy old Winchester power points:
However, take a good look at that target. That was when I was messing around with full length bedding that fwt in a mcmillan. Here's a good pic of that bedding job:
Proof that that particular rifle prefers to be freefloated. Its been my experience that most of them do.