The actual story here is that this was done and written up by a 15-year old high school student. As such, I have to say: bravo, well done!
The claim to „deanonimization“ is stretching it quite far. At best, you could prove a known person (which you know how to contact) was indeed physically in a certain location. This can be useful, but it’s hardly deanon in the traditional sense.
Many VPN providers actually leak DNS, so it might be quite practical even when VPN is on.