pouchdb-all-dbs appears to ignore defaults

Please advise me if I'm doing something wrong. My goal is to use 'allDbs' in my unit tests, which use the memdown adaptor. But I cannot determine how to get this to work. I am trying to the PouchDB.defaults() method to set the adaptor, which appears to work for most normal functions, but this plugin appears to ignore it.

Here is a minimal reproduction case. Save this file as 'test.js' in an empty directory:

var PouchDB = require('pouchdb');
require('pouchdb-all-dbs')(PouchDB);
var MemDB = PouchDB.defaults({
    'db': require('memdown')
});
MemDB.allDbs(function(error, result) {
    console.log(result);
});

Then install dependencies:

npm install pouchdb pouchdb-all-dbs memdown

Verify that we have the proper files in the test direcotry:

$ ls -la
total 28
drwxr-sr-x   3 jonhall jonhall  4096 Feb 11 19:20 .
drwxrwsr-x 132 jonhall jonhall 16384 Feb 11 19:19 ..
drwxr-sr-x 206 jonhall jonhall  4096 Feb 11 19:20 node_modules
-rw-r--r--   1 jonhall jonhall   203 Feb 11 19:19 test.js

Then run the test script:

$ node ./test.js
[]

No output, as expected, but now do another ls:

$ ls -la
total 32
drwxr-sr-x   4 jonhall jonhall  4096 Feb 11 19:21 .
drwxrwsr-x 132 jonhall jonhall 16384 Feb 11 19:19 ..
drwxr-sr-x 206 jonhall jonhall  4096 Feb 11 19:20 node_modules
drwxr-sr-x   2 jonhall jonhall  4096 Feb 11 19:21 pouch__all_dbs__
-rw-r--r--   1 jonhall jonhall   203 Feb 11 19:19 test.js

Notice the new pouch__all_dbs__ directory, thus proving that allDbs() is still using the filesystem instead of memdown. Is this a bug? Is there a workaround?