Omitting fetcher function argument is ambiguous?

The README states:

Note that fetcher can be any asynchronous function, so you can use your favorite data-fetching library to handle that part. If ommitted, swrv uses the Fetch api.

But later also:

To only retrieve a swrv cache response without revalidating, you can omit the fetcher function from the useSWRV call.

So, which one is it? :) Or am I misunderstanding what omitting means in the first case?