Let me start by saying your work looks great.
The guy who said that you are just painting your seats is actually correct. The product you are using just covers the dye already on your seats. I am sure you know that cows do not have grey hides. The process of making your seats grey to begin with is actually a paint type product as well. Technically seats are not dyed they are painted. I found this out when I went to a leather shop to have my steering wheel re dyed.
I have been trying to peel the dye they used on my steering wheel as I no longer use it, and after several years it is still quite well bonded. If your leather pealed it is probably due to improper prep.
Keep up the good work man. I am tempted to buy a car with grey seats to try this myself....Joking.