That page says that eight years after the supposed lawsuit "Batt admitted that the alleged legal dispute had been a publicity stunt and that he had actually only made a donation of £1,000 to the John Cage Foundation."[1] I guess that he plagiarized it is sure even if the copyright claim was not litigated.

1. https://www.bbc.com/news/uk-england-hampshire-11964995

4'33 is not empty! That is a common misperception. 4'33 is the sound of the ambient space around the listener. Each performance is unique.

interesting connection to Cage. Maybe Springer Nature also sees the empty pdf as a form of art? :)