img title="I don't know what's worse--the fact that after 15 years of using tar I still can't keep the flags straight, or that after 15 years of technological advancement I'm still mucking with tar flags that were 15 years old when I started."
I'd initially assumed that it was a mnemonic but yes, listing and appending and extracting together is nonsensical, as tar notes: tar: You may not specify more than one '-Acdtrux', '--delete' or '--test-label' option