This says "for PhDs" but then I found that it's more geared at PhD students working in research groups. A different type of PhD is the tenured professor who has to deal with a large number of projects at the same time. There's research, but there's also teaching, service projects, reviewing/editing, students asking for letters, and dozens of other things. At that scale, it's tough, and I still haven't found a complete solution. I use Todoist, email, Basecamp, version control (Fossil) and a few open source apps/apps I've written myself. I spend about 60 minutes on project management each day - that's organizing projects, not working on them.
And it's not just research, but several different research projects in various stages. I would feel lucky (but also a bit panicky) if I had just one research project to worry about at a time. It's extremely hard to stay organized and focused at the same time.
I think the title implicitly means 'for PhD students', rather than 'for people with a PhD'. I don't know any tenured professors who would describe themselves as 'a PhD'.
