GBot has been executing Javascript and hitting URLs the Javascript generates, for quite some time. And very likely it also evaluates the page layout as it is influences by Javascript, to detect keyword stuffing hidden by Javascript.
I hope this isn't becoming a trend, but lately I see a lot of responsive sites that don't respond to user input. Maybe a little force from Google will stop this trend.
The results of Goog monitoring page load and render times can be seen in Goog's Webmaster Tools and is measured by user's browsers. They started doing that some years ago and I am pretty sure by now it is part of the ranking.
And at the same time they made their own site slower and bloaded. :-/
On the other hand it will finally allow sites that do client-side rendering with JavaScript to be indexed properly, provided that they are responsive - which isn't that hard to do.