UTM to XG Migration - all the migrated FW rule have "Rewrite source Address" check under "NAT and Routing" - Why

Question

Hi, 
 
 I've migrated my configuration from a Sophos UTM (SG) to XG. The migration tool created the new rule but I see the NAT feature enabled because within the Firewall rule form, under Advances>Nat and routing, "rewrite source address (Masquerating)" is check. I have 354 rules so I would really know if its necessary to leave it on before I unchecked that on all of them. 
 Those rule are just to allow traffic from an interface to another, same network but different interfaces and VLAN. 
 I can try it because the other appliances from the cluster are still online. 
 
 Thanks for the heads up. 
 
 Attached: 
 
 Rule Edit

Firewall View:

FloSupport · Accepted Answer

Hi aimnkill 
 This setting simply performs SNAT on the traffic matched to this firewall rule (ex: VLAN 1 traffic to VLAN 2 traffic - SNAT as VLAN 1). This NAT shouldn't be required. 
 Would it be possible to show how the rest of this migrated rule is configured? You will need to define your VLANs via a created network object (though this may have already been migrated). 
 Related community threads: 
 
 https://community.sophos.com/products/xg-firewall/f/network-and-routing/73322/inter-vlan-routing 
 https://community.sophos.com/products/xg-firewall/f/network-and-routing/73278/vlan-traffic-issues/283031#283031 
 
 Regards,