Are these Sanyo ncr18650GA cells fake

You are 90% good to go.
I agree with you that mAh is on the low side for GA cells.
Do you have any other Panasonic cell that does not have many cycles on it?

Try to discharge them at 0.5A

Compare to HKJ Test/Review of Sanyo/Panasonic NCR18650GA 3500mAh (Red)