SAP/Hannah deployments - anyone with experience?

Crossposting from /r/sysadmin in case anyone can suggest a network related reason which may be the cause of the recommendation.

Learned colleagues.

My company has chosen to deploy an ERP using SAP/Hannah (I know, don't go there).

The conslutants involved are insisting that we have to do a thin client deployment for office users because of the "nature of the ODBC connections used, and not being supported on a WAN".

Some information about our "WAN". Our offices, while geographically diverse, are all linked via redundant direct fiber to our core DC (where the hardware, including any RDP instance for SAP, is going to reside). A minimum of 10 gig of bandwidth is available (LACP used for redundancy) on a switched network - ping's and data traffic can hit the DC with sub 1ms RTT's - the DC is effectively just another local segment.

Can anyone provide some insight into why these people are saying there's going to be a noticeable difference in performance between using a Citrix/RDS solution and a client on a workstation in the office?

Thanks to anyone who can shed some light on why this may be so.