GraphHopper not using timestamp


According to my understanding, Graphhopper takes GPX entries, where 3rd argument is timestamp, but map matching result does not change even if I change timestamp parameters. I have static sensors on Highways with postmile distance between the sensors which I want to map and create a road trajectory. I am giving virtual speed to get timestamp between these points.
changing the speed from 30 to 90 does not affect the result. Can anyone explain me if I am doing anything wrong?

Currently only the lat,lon values are used for map matching. See e.g.