So am I right that SWIFT not only gives you a protocol that you can use to interop with other banks, but also some sort of DNS system that tells you how to send money to almost any other bank? This makes me think of the Bitcoin lightning network a bit as well. To reach bank Z, bank A needs to find a route of pairs of banks that can perform settlements, so there must be some sort of routing table to do that. That routing table is probably a service that swift provides and thus if they cut the russian banks from accessing this, they wouldn't be able to figure out how to reach other banks.