Memory used in similar Mac mini

Question

I am wondering what is true and what is not.
I had the local Apple Store upgrade my 2 X 2GB memory sticks that came with my 2012 Late Mac Mini to 16gigs. I was quoted a price that was fairly close to the non-Apple memory I had  researched, plus I was told that there is a life guarantee on these non-Apple memory sticks.  When I picked up the 2012 Mac Mini, I asked to have the 2 memory sticks that had been taken out.  First I was told that they don't give back what they take out.  When I pressed, I was asked what I would do with the memory sticks.  I  said, that my husband has a mid 2010 Mac Mini and if something were to happen to his memory sticks (mac mini was used when purchased) I could use the 2012 memory sticks in his 2010 mac mini.  I was told, in no uncertain terms, that the memory from the 2012 late would not work in the 2010.  When I pressed a little more, I was told that if they gave the two (2 GB) memory sticks back, I would have to pay $20.00 as the non-apple memory sticks they installed, had been discounted $20.00,  This was the first I had heard about any discount.
Did I believe them, no.  Will I go back and  raise cane, no.  Thus I looked up the two memory numbers and this is what I found.
PC3-12800 DDR3 204-pin SO-DIMMs  for my Mac Mini 2012 late at a total of  16 gigs  (8gigs each)
and
PC3-8500 DDR3 204-pin SO-DIMMs =
Mac mini (Early 2009), Mac mini (Late 2009), and Mac mini (Mid 2010) computers have two internal memory slots.
Other than the amount of Gigs per, is there a difference?  Are these interchangeable?
If your wondering why I would not raise cane with the owner... It's because this would be the second time I was lied to, to my knowledge; I don't plan  to set foot in the store every again.
Please tell me what is correct.
Thanks,  Patt

Answer 1

They are not interchangeable. Note the difference in the specifications:
PC3-12800 DDR3 204-pin SO-DIMMs
PC3-8500 DDR3 204-pin SO-DIMMs