Basic physics. Newton's Third Law of Motion. For every action on an object, there is an equal and opposite reaction. C'mon armedsask, you make gun stuff. You should know simple physics principles.
Caseless still recoils. You eliminate a step out of the cycle, but it doesn't mean there is no motion or energy. The bigger the bullet, the more energy needed to push it. The more energy needed to push it, the more it's going to push you, the human operator. Gatling Guns are an example of not requiring a reciprocating gas system for ejection and high rates of fire. Even then, for control by humans, rate of fire has to be reduced (that and ammo usage). While yes, bullet size doesn't matter, the HUMAN factor does. If humans were not such fleshy little things, we could all walk around with 1000rpm 25mm auto cannons and fire mortars from our legs, but we don't. I guarantee you, that if they up the calibre for the G11, it will not fire the purported 2000rpm. It will be more than traditional firearms, but not the same as with 4.7. And also, that rating is on burst. Burst, unlike automatic or single, are more hypothetical than actual. Just like the AN94's 1800rpm.
And speaking of the AN94, to achieve it's 1800rpm 2 round burst, it uses the recoil of the first shot to cycle the the whole action with barrel in which upon rearward motion, strips a cartridge and presets it for chambering, and the forward motion, sets it the chamber. That whole mass of the action, rather than just bolt and bolt carrier, reduces the overall energy felt by the user by a good amount. The G11 does not have this extra mass or reciprocating system. Any recoil is going to be felt by the user.