I found this document about Savage 99 Parts from serial number 90,000 to 1,000,000
Ther are no significant changes to the firearm so I do not see how there would be a difference between the early and late models G.
Perhaps the information you have received/heard has to deal with the 'Featherlite' model vs the other models.
I would appreciate and input from others who think otherwise or may shed more light on this subject.