samba - Jul 2018 - Pam support

I have been looking at Samba's pam support and have noted that to enable it
you need to set encrypt passwords to no, what would be a use case in this
instance as it is very insecure? Has anyone implemented it and why? Also
when encrypt passwords is set to no the pam modules do not get called
because the plaintext password is null and we get a NT_STATUS_LOGON_FAILURE
which I'm guessing is due to the smb clients running in secure mode, would
that be a correct assumption?

Thanks for you time

kai