It seems like the author isn't interpreting it the same way at all, because "(undefined . id)" would be the same morphism as "undefined" by the criteria on the

It seems like the author isn't interpreting it the same way at all, because "(undefined . id)" would be the same morphism as "undefined" by the criteria on the wiki page, and then the author says that they must be different because you get different behavior when you pass them to "seq", which is a radically different set of criteria. Which is exactly what is addressed by the wiki page... you get different behavior when you use "seq" on two different things which are the same morphism. The wiki page even uses almost the same example.