Yes! I see this all the time when setting directions for provincial parks and other "remote" destinations. It never occurred to me that someone would blindly follow them.
All that being said, changing the directions so it ends up at the visitor center is probably a good choice, regardless of how few people actually were or would be confused.
I'd consider a shaded-in area with wiggly outlines, big enough to be path shaped, that just says "walk". That conveys "you need to get yourself to this pin, and we don't know how to help you".
Obviously, mapping a destination on an island with wiggly lines through the water which say "walk" would not be useful, but wasn't the situation I was envisioning.