We experience the same issue. Open up a case with support and support confirmed there is a known bug on EMS configuration for IPsec.
Below is the support statement and bug number for version 1.2.2
"we seen a bug 0439370 reported for not able to seeing username on Forticlient for ipsec connection as configuration sent through EMS. "
If you are able to enable xAuth through the XML, can you point us to the correct XML field?