Theres another angle to this which has been overlooked by the article writer.
That is namely that the onus is on the publishers to ensure they use companies that are GDPR compliant, if google is not fully GDPR compliant then the publisher has no choice but to move their stuff elsewhere.
The ultimate consequence of google not being fully GDPR compliant is that all EU companies will have to move elsewhere. Advertising-wise thats going to hit google really hard.