Thanks for pointing these out, which I had not seen before.

Neither blog seems to have almost any mathematical content, and the posts seem few and far between, so I don't think that they budge the bottom line. Even in the case of Gowers, the average number of mathematical posts is about one a month.

Also, the category "Fields Medalists" is in some sense cherry-picked, in that it happens to include Gowers and Tao in particular: if one broadens consideration to all of the prizes that I listed, the fraction of bloggers is much smaller (though the winners of the other prizes also tend to be older).