I asked a few customer support employees, they don’t know and advised to ask on forum.
I know official rules about multiboxing to prevent bots who use the same inputs on a few different instances. However what I’m doing is 2 gamers at the same time at the same machine with seperate keyboards and inputs. It’s equivalent of virtual machine or ALT+TAB on different instances of wow. Is that allowed?
Update about topic.
Most likely it is allowed. However, they are not sure. They don’t know how to confirm that with technical team, that makes anticheat software.