I think kcott is on the right track, it's a documentation error.

In

If you omit the LIST, $_ is used; to use FILEHANDLE without a LIST, you must use a real filehandle like FH , not an indirect one like $fh

LIST is meant to describe the ARGUMENTS ( i.e. FORMAT, VALUES) to the function (or method i.e. FILEHANDLE->printf(ARGUMENTS) ), like you can see in the following example

  DB<100> $_=42
 => 42

  DB<101> printf
42
  DB<102> printf STDOUT
42
[download]

(tested with 5.10 which didn't even document the use of $_)

So LIST should be replaced with "ARGUMENTS" in the quoted part.

IMHO the other occurrences of LIST should be replaced with "VALUES".

that is

 printf FILEHANDLE FORMAT, VALUES
...
[download]