Except for the first crop of my Meiwa, where the fruits were very bland and dry, my kumquats have all been pretty consistent from year to year. I have multiple Changshou/Fukushu trees. The only real difference I have seen with my Changshou crops is that they make larger fruit as the trees grow larger (the larger fruit is worse, in my opinion) and they are seedless when there are no pollinators during bloom.
I can't explain why yours might be different, but it isn't something I would consider common.
