Small performance win: https://coq-speed.mpi-sws.org/d/1QE_dqjiz/coq-compare?orgId=1&var-project=refinedc&var-branch1=master&var-commit1=a09a919f04f114de27a324641b36edbdd5242ed0&var-config1=build-coq.8.17.0-timing&var-branch2=time%2FiProp_to_Prop_primitive_proj&var-commit2=f43db09c385c0212f59c894e694ae730dea86ac3&var-config2=build-coq.8.17.0-timing&var-metric=instructions&var-group=(.*)