Some historical context might help: when this recording was released, the copyright lobby was still issuing takedown requests and blocking views on YouTube videos and websites. So in some jurisdictions this recording was the only one easily available to use.

Also, the open source and digital first nature of the transcription - the first high quality transcription in musicXML - meant that this project enabled lots of "downstream" projects, such as the first braille edition of the Goldberg variations.

Just because a piece is public domain doesn't mean it is accessible!