"Oh look, new version of ancient and well known weakness 'invented'"
That's a summary of the article. It was known decades ago that things could be subverted by the simple act of running a rogue DHCP server on a network. There are ways of mitigating that risk - one being to filter DHCP packets at the switch level (why aren't Google doing this ?) so that the rogue server can't get packets to clients; another is to simply monitor the network and manually locate and "terminate with malice" any rogue server; and another is to use secured messages (but that requires pre-configuration of the client which partially defeats the object of DHCP). It's also been known for decades that you can substitute a DHCP packet flood for running an actual service.
So yes, it's a known and solved problem - the only "news" is that in the 21st century it's a problem on a service run by an outfit that you'd think was big enough to employ grown ups to run the networks. The fact that there's weak randomisation involved is pretty well irrelevant - that's really only a mild protection for "idiots didn't do any of the above well known network level defences" and hence allow DHCP "server" packets to come from a device that isn't an authorised DHCP server.