Follow-up HG repair...I was surprised to find ??

Did the full HG repair with pulling the motor out..what a pleasure doing it outside of the car with the help I have received here..just so much easier to clean and care.....Wanted to say that I was very surprised to find the gasket material (viton or whatever subaru uses) in my coolant overflow bottle..it did explain why the coolant turned black, but not from oil mixing in.. also, I am bewildered, after changing my coolant yearly, as to why that so-called viton material would just peel off the steel gasket and only around the openings that coolant flowed thru...Also the top and back side edge of the block showed corrosion (small pitted areas)...Strangely, around the openings of the cylinder and oil drain holes were very solid and could not be peeled off...definitely a poor quality gasket..anyway, I went with the "six-star brand" and hopefully it will hold up better..time will tell...