Most repeaters do not work in that mode. What you are running is a repeater that is acting as a router. Most repeaters you find are running as a bridge. This is they problem with the misuse of the term "repeater".
It really depends on the device. In someways it is nice to have the option yours does when there is no other way to get it to work. Most "repeaters" do not have this option and in cases where you do not have access to the main router you will never get some repeaters to work.
Normally the feature that is used to make a repeater function in bridged mode is to use WDS to connect to the main router. This allows multiple mac addresses to be passed over this connection but you many times must allow WDS in the main...