Here's the PDF. Perusing through it, they seem to say more than just that. At first glance, it seems to boil down to whether or not their measure of complexity is a valid one, and if this complexity maps to current known evolutionary timescales. Evolutionary genetics gives us data for this as far as I know. Their measure of complexity is: Sharov is one of the authors here. Here is the source cited, it's a slide deck and the last two slides are basically the figures in this article. Although the idea would be a very satisfying way to deal with the apparent celestial silence, since the authors couldn't find a better source for a measure of complexity, it's my guess that that they just have that slope wrong.measured by the length of functional non-redundant DNA per genome counted by nucleotide base pairs (bp), increases linearly with time (Sharov, 2012).