have owned 3 different 10/22s and fired many others. I don't recall such a widespread difference. There have been many changes made, even to the trigger assembly (e.g. ejection button, polymer in place of aluminum etc.)
As with any production line item, precise duplication is an extra cost. I would lay such differences to roughness of the individual parts involved. I have never purchased an aftermarket trigger, even for the 2 full trick out 10/22s I built.
My gunsmith grandson can take the original and make it as effective as any aftermarket trigger assembly available, so naturally I just let him do it !
About 2 years ago I bought my last "10/22"...but it isn't a 10/22 at all. It is a TCR 22, and I am very pleased with it!
..And yes, even though the trigger was quite good, I still mailed it to my grandson, so he could do his "magic'..now it is superb.