There are no Devs on the Support forums so you won’t get an answer from one. The only statement they have made is the Support Article and the Forum Post.
that use of all software or hardware mechanisms used to mirror commands to multiple World of Warcraft accounts at the same time, or to automate or streamline multiboxing in any way may result in account penalties.
Even if you are using a keyboard and mouse, if you use anything at all to streamline the process, that is against the rules. That includes hardware solutions as well as software solutions.
So were you using a macro to switch game instances and binding a key cast or cast sequence to the mouse wheel? Yeah that is going to get you in trouble if that is what you did. That is def automation.