Chivalry demanded no less than stopping to see if the stranded witch required assistance, and when he landed and she hauled out a wand he held his hands up in the universal sign that he wasn't a threat.  She cast a quick lumos and if it let her see who he was, it did the opposite as well and he let out a low whistle. Greg Goyle hadn't aged well, but Ginevra Weasley had, and she'd been beautiful to start.