Not sure what's special about my Evernote installation, but after some debugging I found that appending doesn't work unless I do
cd ~/Library/Application\ Support/
ln -s ~/Library/Containers/com.evernote.Evernote/Data/Library/Application\ Support/Evernote
( ~/Library/Application Support/Evernote doesn't exist on my computer )
Did I say that this Workflow totally rocks?