So, it seems that "r > g" is less of a question and more of a generally accepted statement. I'm not an economist, but a cursory review of economist whitepapers (here's one[0]) indicates that most don't dispute the "r > g" assertion, but instead just say that "this is a reasonable state of affairs", or "it's a problem, but the solutions are worse."

[0] https://scholar.harvard.edu/files/mankiw/files/yes_r_g_so_wh...