Probably just to make sure that Blender remains available for their platform. If popular programs aren't available for their ARM / macOS platform, it can hurt them. Good for Blender.
Not a problem. M1 blender benchmarks were already smoking the x86 Macs, despite the fact Blender was running on M1 with Rosetta.
A native build is obviously better of course. But OSX ports are a bigger deal, in general, than the CPU architecture.