Mahoney does not say this. He does complain that writing is difficult because there is so much richness to distill. But he praises collaboration. Collaboration brings gains in shared writing and reflections. Sharing enriches the context, encourages us to see more, to build on each others' shoulders.
Collaboration brings gains in an understanding of different perspectives and contexts.
Others bring different contexts and perspectives to our work. Application of theory to practice is best done alone because it requires a thorough understanding of one's field to see the possibilities for application. Often the outsider can bring greater insight when working in conjunction with those who are experts. The outsider is often not constrained by the discipline's traditional patterns of thought and ways of explaining things. Collaboration requires that each collaborator become expert in the shared field.