I imagine there is also probably some other prior art. But that's a very well known one.
They also claim that it affects all VPN clients in the headline, yet so many such clients setup firewall rules to block traffic to/from the physical interface as they acknowledge in the write-up. Most of the VPNs that are claiming to hide your identity or where such cloaking is important tend to implement that. I'm sure plenty of setups don't have it enabled by default, but I think it would have been productive to document what percentage of leading personal/commercial and corporate VPN solutions have this enabled by default.
A good write-up and explanation for the lay person, but I think the headline over-sells it a little bit given the number of clients that would prevent most of the data leak with those firewall rules and not acknowledging the prior art in this area.