Unfortunately, that's exactly the argument that Cruz is using to continue Block 1B development.
Hopefully, when/if Starship starts refueling successfully, his tune will change. There is a case to be made that killing SLS before something has been proven to be able to take over its mission would take an unnecessary risk.¹ But F9/D2 + even a rudimentary HLS Starship (it needs the crew module to work, but it doesn't even need to land!) is a complete replacement for its part of the Artemis conops. That's something that could be proven out this year.
We've already flushed a nice chunk of change down the toilet for FY26 EUS and ML2 development. But the FY27-28-29-30 out-year money has only been obligated. That's nothing a nice rescission can't fix.
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¹We'll leave aside the fact that SLS/Orion has nothing to do without an HLS, and Starship is required to do that.