I read your comment as strongly sarcastic. Do you mean it that way? Because it looks to me like they are very up-front about how iffy some of this stuff is. So what's the problem?

  The trouble with self-help advice is that it’s often based
  on barely any evidence. 
  ... [however] we’ve found that there are a number of
  evidence-backed steps that anyone can take to become more
  productive and successful in their career...

  So we’ve gathered up all the best advice we’ve found over
  our last five years of research.

  In many cases, the evidence isn’t as strong as we’d like.
  Rather, it’s the best we’re aware of. We’ve tried to come
  to an all-considered view of what makes sense to try