I was monitoring CPU & GPU while exporting a timelapse sequence:
As you can see, GPU is idle when exporting images - CPU does all the work. So GPU is used only when moving the sliders in the Develop module for a fast preview of an image you are working on, but for export it isn't used.
What's your opinion? I'd like to have exports accelerated too. I was hoping for it. Exporting timelapses is really time consuming.