Hey.
I just pushed a new version that fixes some issues with tabs and the files field. It should now work exactly like accesing images from within a structure field
To access images of a builder fieldset you can use something like this:
<?php foreach($data->images()->toFiles() as $image): ?>
<?= $image->resize(100) ?>
<?php endforeach ?>
In the old version, this did only work when not having tabs in the fieldset.