The gas system eats up some recoil...but not all of it, she still has a pretty decent wallop to it. It's by no means a heavy rifle, it only weighs between 8 and 9 pounds... roughly about what an SKS does, looking at it you would think it weighs what a Garand does, but for the caliber, it's a light weight rifle. So in a round about way, it's a x54r SKS, just a little longer. One of the reasons you see alot of AVT stocks used in place of SVT stocks is the wrist. The AVT stock was a beefier design, it's substantially thicker in the wrist, the SVT stock would typically cracked at that point.
I think the reasoning for so much gas adjustment is variance in ammo, ammo manufacturers, temperatures and maybe even altitude. All of those play into gas pressures when fired. And even though the sights are calibrated for light ball, you could use heavy ball when you get it adjusted correctly. Usually you start low at 1.1 setting and work up till the cases drop 5-6 feet from you, and it's good to go. Even going from one ammo manufacture, modern or surplus to another would sometimes it needs recalibrating. Now with a really worn rifle, or rifle with a corroded up leaky gas system, you can sometimes go a setting higher to compensate for lost gas volume and get it to cycle, but your getting to the point of diminishing returns.. at this point your just gas eroding parts, slamming parts around, your better off to just fix it or quit shooting it.
Think of the gas system like difference the Ljungmann AG42 and the Hakim.... The Ljungmann with no gas system adjustment was pretty much constricted to Swedish 6.5mm military ammo with close tolerances and high quality control it was designed for.. The Hakim, you could use Egyptian, German, Czech, Romanian, all most any 8x57mm round (with the exception of Turkish) if you found it. Which is what Egypt did, they had stock piles of ammo from everywhere in Europe after WWII and took the Swedish design, altered it and built an adjustable gas system rifle that could utilize the massive hodge podge of ammo they had.