It has todo with the order, how tags are parsed.
MODX is trying to build the url from placeholder [[+linkto]], which isn't replaced at this time.
When using a tpl-chunk, getImageList does replace the placeholder at first, and MODX can build the URL while parsing the makeUrl - tag in the next parsing-step
That makes sense.
It might be helpful to add a note about this in the documentation.
Thanks for the help!
