Yea, this issue has been pointed out several times, but it has yet to be addressed.
There seems to be a general issue of friction in-between-rocks that isn't very realistic. Too much energy gets lost on big weight shots, while too much is conserved on the back-ring/hack weight shots. Very make-able double take-outs becomes to flat, while the steep angle doubles that are supposed to be near-impossible are too easy. To me it seems like the friction between rocks have been simulated all too much to look like that of pool balls, while the actual friction between granite rocks should be much higher.
I for one, would love to see this game become even more realistic. It is already the best online simulator available, and lots of real life curlers play it. But the tendency is that it's tough to hold on too all the real-lifers, leaving for some reason a bunch of eastern Europeans and south Americans... It's a petty, and part of the reason is that the physics deviation makes tactical dispositions quite different from real curling.
Curling stones are gliding granite rocks, not rolling pool balls!