of course it was!
what else could be a larger difference than that
it makes the gun function and feel differently and practically everything is changed regarding ballistics, effective range, and probably even the sights too for different range settings
While that is true, nothing about the gun was changed to accommodate the round, the round was introduced
for the AK-74.
It boils down to the round being developed with the intent of working in a lighter, more reliable, better rounded AK.
Does the introduction of a new round make a big difference? Yes it does! but when the round was developed to work for a gun that was already being modified with certain things in mind, those other modifications that the gun goes under to meet goals outweigh the difference.