I never used LANMAN, but the spec makes for some interesting reading...
> NOTE: Due to a temporary restriction in CMD.EXE, it is not possible to use the DIR command on a UNC pathname, as in DIR \ \BIGSERVE\ANYNAME. This will be fixed in a future release. The DosFindFirst API call will accept UNC pathnames.
I always wondered about this... apparently the restriction carried over to the Windows port and was never fixed... maybe they didn't want to bloat cmd.exe with needing to "NET USE" UNC paths behind the scenes? Who knows!