I think the situation is: Cranelift - experimental, quick to port Ion - production, slow to port So Firefox on Apple Silicon got Cranelift first, but only in

I think the situation is: Cranelift - experimental, quick to port Ion - production, slow to port So Firefox on Apple Silicon got Cranelift first, but only in nightlies, and will soon get Ion in release builds - "become the new default" means it will replace the baseline compiler.