They're cautioning against drawing statistical conclusions from it. That doesn't mean the log-log plot isn't more useful than the linear plot. Also they seem t

They're cautioning against drawing statistical conclusions from it. That doesn't mean the log-log plot isn't more useful than the linear plot. Also they seem to be talking about a power law distribution, whereas here we're talking about the dependence of two variables. As a first step plotting them on a log-log plot and saying 'yeah, looks straight' is fine. Among other things this tells us the dependence is suspiciously close to a cubic root law, which could possibly be justified using dimensional analysis.