Yes, the remains in Herxheim are a sign of cannibalism in early humans. The human bones were found tossed in in along with the bones of other animals that were eaten, and the patterns that the bones were in indicates that they were often tossed in a leg or an arm at a time. Such a practice is far more consistent with a cannibalistic culture than one that just wants to bury their dead.
Yes, the remains found in Herxheim, in present day Germany, are a sign of cannibalism by early humans. Although cannibalism is rightfully seen as an unsavory practice by most people, it has been practiced in many societies throughout the history of humanity. It is not surprising that evidence of this practice would be found in Germany.
Studies do seem to be quite clear that humans were butchered and eaten at the site of Herxheim. As normal members of society we can only place trust in what the scientists and researchers say. It is certainly possible that cannibalism took place in early humans. The analysis of the remains may be grim, but it shows how much humans have changed over the last 7000 years.
The remains in Herxheim beg more questions than they offer answers. Without being able to talk to the people, we don't know what really happened in that society. Cannibalism might not have been the standard practice, but it might have been necessary in order to survive. There are too many unknowns to know for sure.