It's an option of the Stand-Alone Addon Manager INSTALLER.
Previously, it would automatically download all current version of all AFCADs for all the FSDT sceneries that are found to be installed when it runs.
Now, it will ASK if you want to update them, so in case you modified them and are happy with your changes, your modified files won't be overwritten automatically anymore ( a backup was made in any case, so nothing was ever lost, but you still had to restore your files )