Exactly right, Schmoodle! It's in there twice, once in the dough, once in the filling. In other recipes, it might be written, "1/2 cup maple syrup, divided" but this seems clearer to me (and it's how they wrote it). Thanks for asking, though Evil! It does seem like a typo at first.
Someone mentioned these in the daily and called them "pumpkin oatmeal bars" and that had me thinking...we could probably just substitute pumpkin puree for the mashed sweet potatoes--less work! I bet that would be good too!