I have only had a couple retipped cartridges myself.
One bought already retipped with about 50 hrs on it that I had owned the model previously. Also one I had retipped myself. Both sounded very good and very similar to the originals but with a very slight loss of the upper shimmer even after a few hundred hours time. I wouldn't word it that you can't or couldn't tell the difference but rather accept it isn't the same original cart so changes would be or should be expected. To what degree is the real point.
I'm usually more suspect of ads for retipped with zero hrs use claimed and put up for sale without knowing what you payed for. I haven't had much experience with used carts though.