There are a few complications to the rule that path names are always parsed on the client. For example, symbolic links could have different interpretations on different clients. There is no answer to this problem in this specification.
Another common problem for non-UNIX implementations is the special interpretation of the pathname, "..", to mean the parent of a given directory. A future revision of the protocol may use an explicit flag to indicate the parent instead - however it is not a problem as many working non-UNIX implementations exist.