Some platforms (e.g. Linux) do not distinguish network interfaces at the packet level when they are connected to the same network. When enabling the setting “Rules can apply to specific interfaces” (under Policy > Interface Types) on these platforms, firewall policies that attempt to distinguish network interfaces on the same network will result in only one of the policies being applied.
It has been confirmed that this occurs when the interfaces are on the same network. Otherwise, the implementation of policies works as designed. This is a documented issue on Deep Security 9.6.