How is a Universal 2 binary different than the original Universal binary? Why is a new format needed?
Universal 2 Binaries
The original Universal binary allowed compatibility between Intel and PowerPC architecture slices. The new Universal 2 binaries contain architectures slices compatible with Intel and Apple Silicon.
But in both cases they're just multi-architecture Mach-O binaries. No real change in format other than what the slices in it are.