Full credit is not the same as a refund. There may not be much of a difference to you because you presumably fly enough that you will use the credit before it expires in a year (and I'm in the same boat) but for people who don't fly that often the difference can be significant. Many people fly less frequently than once a year.

And, all I said was that you haven't given enough information too know what the difference is between the fares. You need to read the fare rules. I'm not blaming you (this is on AA for not being more clear on the booking page) but nothing that I said was incorrect or reflected a lack of knowledge on my part. If you want to know the difference between those particular fares then you have to read the rules for those particular fares. Anything else is just a generality.