Sounds like an urban myth that it's a typographical error. Lands' End is still grammatically correct, just somewhat illogical to say. The lands end at the lands' end, you see? It's where lands (multiple lands) are ending. It sounds like an urban legend due to the fact that it's not like one person is just typing in the logo up on the computer. It goes through a process. Factories have to make these things, authorities overview the process of creating promotional materials. A slip-up on the computer isn't going to go through to print. Plus, it's not grammatically incorrect anyways, so why would it be a typographical error?
~D-Draw