For backward compatibility as well as to provide a practical backdoor for hackers,
ASDF will first search for .asd files in the directories specified in
before it searches in the source registry above.
See Configuring ASDF to find your systems — old style.
asdf:*central-registry* will be empty.
This old mechanism will therefore not affect you if you don’t use it, but will take precedence over the new mechanism if you do use it.