I don't believe them. If you look under <learn more> in the configure page for the mac mini you DO NOT FIND the following paragraph:
"Note that MacBook Pro with Retina display comes with 8GB of memory built into the computer. If you think you may need more memory in the future, it is important to upgrade at the time of purchase, because memory cannot be upgraded later in this model."
This leads me to believe that the ram IS UPGRADEABLE.
Thinking the same thing