The same works with the 'Select another layer for reference' magic wand tool
The 'refer another layer' fill tool, which is great if you use lineart regularly but hate doing flats it has a close-gap in it, so even if it isn't a perfectly-closed area, it still fills (you'll still need to clean up tight spaces, though). Some honorable mentions, too, which are easy to figure out, but could be useful to people new to or looking into trying the program:
