You are dead right regarding springer recoil however there is a significant fundamental difference between gunpowder artillery recoil and springer airgun recoil. Regarding real artillery I have 30 years experience live firing muzzle loading artillery in competitions. Like any firearm, artillery recoil is usually insignificant until the projectile has left the muzzle.
View attachment 288062 This above photo is a "unicorn" blind luck photo. The projectile is exiting the muzzle at this very instant. The grey "flower petals" at the muzzle are gases exiting around the projectile via the seven rifling grooves in the cannon. The firing lanyard is still springing back towards the cannoneer who fired the gun. The vent blast is only three feet high and all fire. If you look at the gun trail you will see it is squarely on a piece of plywood which we use to reduce friction in traverse sighting. Recoil has not even started in this photo and the projectile is at the muzzle. Next photo:
View attachment 288063 The gun is in recoil and from the muzzle blast the shell is on its way to a target a half mile away. The crew member's images are sharp but the gun wheels are blurred. Also note that the trail is no longer on the plywood as in the first photo. The recoil is approximately 6 feet.
Free recoil of artillery does not effect accuracy. The reason for free rolling recoil with the CW/muzzleloading guns and spring buffers in modern arty is to allow the guns to be operated without recoil stresses breaking things. Spring buffers also allowed recoil spades to be used so you don't have to manually roll the gun back into battery after each shot.
A springer air gun goes "sproing, slam, rattle" while the pellet is still in the barrel. The loose hold allows a springer to recoil the same way with every shot. With pellet still in the barrel the loose hold is critical for accuracy by making the recoil derangement as consistent as possible shot to shot. Regards, Badger.