So no data, just a generalization. Okay.
Whether the barrel is fixed to the frame or moves with every shot does not predict how well a gun shoots. There are too many other variables involved. Accuracy is usually gun and ammo specific. Check out any accuracy test with gun reviews and you'll find a wide variation in group size with the same gun.
You obviously won't listen here but I'll throw this out.
The barrel not moving about means that .....the barrel is stable. It doesn't mean it's a huge difference but the tolerences mean it'll be a little different. Ever notice the difference in a standard auto when you rack the first round in vs the 2nd round cycling? It's not inches different, but it doesn't take too much angle to make a half inch difference with a 4.5inch barrel at 15 yards either.
It's also why target 22s are usually fixed barrel as well