This issue is resolved by updating to v1.61.3. It is a bug in the Contacts object actually.
I mean Node.JS only initiates the call. It is not taking part in the call. The call is between the 2 parties. I've drawn a simple diagram here to show what I mean.
To add on to this, even though it might not make sense to make a call from server-side node sdk to another rainbow contact, it would be useful to be able to initiate a call between 2 other rainbow ...