Comment by simoncion

Yes on the same computer. Pretty much every multicast-capable host has a unicast address and has multicast groups that they join when they get an IP address. [0] Edge routers almost always have -at minimum- a global address and a "site-local" address. Any host that has multiple active interfaces can have multiple "categories" of addresses assigned to it.

You might also be unaware of the fact that network interfaces can usually be assigned multiple IPv4 addresses, just like they can be assigned multiple IPv6 addresses.

> ...the application does not have to figure out which one it has to use.

You might be surprised to learn that that's the job of the routing table on the system. Applications can influence the choices made by the system by binding to a specific source address, but the default behavior used by nearly everything is to let the system handle all that for you.

[0] You appear to be unaware that multicast addresses aren't assigned to a host. I suspect you're unaware that IPv6 removed the special-case "broadcast" address. It's now treated as what it actually is; the "all hosts" multicast address.