Transparent mode only performs DNAT so that's all you'll ever see in that scenario. For one armed mode, both SNAT and DNAT are performed, however, if you're looking at the NAT config on the edge, you'll still only see the DNAT rule that the LB creates unless your virtual server has acceleration enabled (otherwise the L7 LB engine is actually establishing a separate backend connection to the pool member so not utilizing the L4 NAT functionality and the DNAT rule you see in the UI is effectively a placeholder to prevent users from configuring a conflicting rule).