well, that's true. But since it's configurable we don't have to leave them out, because we can configure them in pam_mount.conf.xml. It just leads to misunderstanding if there are some options you can configure and some they are already default without knowing about. In addition: most howtos you'll find for samba and pam_mount will tell you to configure uid and gid in the volume definitions - even if they (e.g. https://wiki.ubuntu.com/MountWindowsSharesPermanently#Mount_password_protected_shares_using_libpam_mount_.28Ubuntu_9.04.29)...
uid and gid should not be default options for cifs mount