This behavior occurs if the version of fstyp that is called does not support VxFS. This indicates that the OS-native version of fstyp, which does not support VxFS, is being called instead.
Use the version of fstyp that is installed with VxFS. On a typical installation, the VxFS version of fstyp is located under /opt/VRTS/bin/.
Note: If this is not included in the PATH statement for this account, it will be necessary to include a "./" before the command when attempting to run it directly from the path.