Seems like there is a way to pet your beloved pod on PC as well.
How To...
- Take control of the camera with mouse.
- Rapidly move your mouse in small circles. It should work after few times.
That's it.
Makes me wonder whether it was intentional or just a leftover from PS4 version, due to DS4's touchpad. Well anyway, here it is. Hopefully they won't remove it in the future.