- A coinjoin participant does not use a separate Tor identity for input registration and output registration
Coinjoin participants use separate Tor identities by default. Look on the code I've linked above. They'd have to deliberately mess with the source code of Sparrow or Whirlpool-cli to not use separate identities.
I don’t know what is meant by "NewIdentity" in the Samourai code from your links. Perhaps this is the creation of a new connection to the coordinator, however, I repeat, the created connections are sent through tor interface and can be exited there from the same IP address (exit node).
First of all, there is no exit node, because you're connecting to a hidden service, not to the clearnet:
https://github.com/sparrowwallet/nightjar/blob/08fd60cd5256ce4842701c6c179c18f997fd252f/src/main/java/com/samourai/whirlpool/client/wallet/beans/WhirlpoolServer.java#L19.
Secondly, just because there is no "Tor management interface", it doesn't mean you can't have different identities. If you have the option to establish connection with Tor, then you also have the option to re-establish it under new circuit, therefore under new identity, which is literally what Sparrow and Whirlpool are doing:
https://github.com/sparrowwallet/nightjar/blob/08fd60cd5256ce4842701c6c179c18f997fd252f/src/main/java/com/samourai/whirlpool/client/mix/dialog/MixSession.java#L265.