They certainly can but the end users likely can't. I am sure there are a lot of projects that make Arm assumptions and porting isn't as simple as changing compilers. And is Risc-V tooling as mature as Arm? Doubtful. So releasing a pure Risc-V micro is Risc-Y at this time.

However, giving end users both in the same chip eliminates any risk because it allows the Risc-V tooling to develop at the same time. And if that development fails, oh well, the Arm cores will keep working and the next tapout might exclude the Risc-v cores. Life moves on.