I'm pretty sure most of asm.v3 got folded back into asm.v1 and asm.v2 discarded with Windows 10 1803.

Look at the example given at the page you linked to, or pretty much every newer example anywhere at doc.microsoft.com these days. But you can probably still freely decorate with asm.v3 for backward compatibility.

It does seem arbitrary to the point of near chaos though. I can't find anything that authoritatively lists tags and namespaces for Fusion manifests.