I think that they were just frugal at model change time and used available parts. Years ago I thought they were aftermarket guns but it gradually became clear that they are factory made. I prefer the 300 stock for it's slimmer lines and I think the sleeveless guns are a great find . If one is serious about 10M you need a PCP, if one enjoys beautifully crafted older 10M guns you hit the jackpot!!!. It will shoot better than 99.8% of us and we get to enjoy it's walnut and bluing. I have a 150 T with no sleeve and love it's balance and weight.
I think you got a perfect combination in this one......GB