Earlier quoted context omitted.
macOS can support all three of the platforms above with a single fat binary.
You are mostly right, I had forgotten about fat binaries. However, 10.6+ only supports x86{-32,-64}, and and 10.8+ only supports x86-64 [0]. Having Windows 10 (?) support 4 architectures is a feature, in my opinion. But, I'd still agree fat/universal binaries would be a usability enhancement. [0] https://en.wikipedia.org/wiki/Universal_binary
Probably these new ARM machines won't support legacy hardware, though that may not be relevant nowadays.