Two separate concepts here
Anycast may have the ability to deliver different answers to different queriers, but that is not what happens in the root zone.
When the root zones moved to be mostly hosted on anycast nodes, so that it could better stand up to DoS attacks and provide faster, more local responses, the root servers all still serve up consistent data.
Serving up different answers is usually geo-specific DNS, which is sometimes (not always) implemented using anycast. However there is no requirement for the answers to be different. In the root zones, the answers are all consistent, but served up with anycast.
It is the serving of different answers to different requesters that was considered heresy and was complained about, not the serving of DNS via anycast itself.
I think the article does not separate these two concepts at all.