the authors tackle a long-standing problem with lots of data, the methods are mainstream by the most quallified specialists..

I'm not a specialist in this particular question any more, but my impression is the results have a surprisingly large contribution from the the temperature.

We've known for a while that the 3 major influences on topography are
(1) Crustal thickness
(2) Composition of crust and mantle, and
(3) Temperature

Our older prejudice was that the crustal thickness mattered most by at least a factor of two over the influence of the variation in crust and mantle composition from average crust and mantle composition and temperature.

So there is something new here, although perhaps not as much as suggested by the article.