I think gps tracks are not just accurate enough for sprints. And map calibration/accuracy is not that perfect either for various reasons, like for legibility exaggerations. I believe the only way to get the track match nicely the map and video is editing track a bit. Usually when I have geo-referenced the map, I drop the gpx file on geo-referenced map image and drag-edit track to make it match well enough for the video. that may take a minute or two to make it perfect, but thats short time compared to the time video processing takes.
In low light conditions some cameras tend to start doubling frames, two consecutive frames becomes identical. That gives it longer (longer than framerate allows) exposure time. I think thats what you see in that video, no post processing can make that smooth if camera moves. For stationary camera that method is just fine.
The editing function for GPX tracks at
map.routegadget.net is very nice. I'll use that in the future before I use mapflixer.