Yes WM they do. But politics is what it is.
Starship is designed to take 100 people to Mars. Not sure how viable that number will be but it could certainly take 100 to the moon.
The SLS and the Artemis moon transfer module is designed to move 7 people to the moon. Artemis was envisioned more than a decade ago before the re-usable Falcon 9 existed. They carried on with that delivery regardless up until the launch earlier this year which orbited the moon with the Artemis module.
Meanwhile SpaceX created re-usable boosters and took over the space launch business. Created re-usable cargo dragon modules for the ISS supply then re-usable dragon crew module for crew to the ISS. Then they started on Starship. An interplanetary transfer vehicle for Mars. Different goals.
Now we have two systems to do the same job. One which is fully certified with NASA and the government and one which is in ultra rapid development but not even certified for the first test launch yet.
Starship HLS will go to the moon and then stay there. Being refuelled from a fuel depot which needs to be delivered to the moon and refilled as needed. Artemis is designed to launch the crew, dock with the lunar gateway station (in development), the crew will transfer to the HLS, land, do what they need to do, ascend, dock with the lunar gateway again and the Artemis module will return the crew to earth.
See diagram.
The thing is that Artemis will send a crew to orbit the moon in 2024. Then a crewed landing in 2025/6. In that time SpaceX need the Starship functional to launch the HlS, refuel, send fuel to the moon and send HLS to the moon. NASA has to deliver the Lunar gateway and more SLS launchers to get the crew to the gateway.
Where SpaceX will be when their Starship deliveries are done is open to debate. The system is not designed to send stuff to the moon, it is designed to be the workhorse for building a city on Mars.
So there will certainly be redundancy and money loss. We shall see.