The truth
When it was all said and done, Jan came out of a coma, that fact is undeniable. The only thing that was up in the air was how long he was asleep exactly. Also, what did he really see when he was asleep for that long? Maybe he did actually gain some powers?
The only person who really knows the truth is Jan and his family. After all, if he was lying, they would all have to be in on it together. They all stated that he was asleep for nineteen years and none of them ever changed that story. So maybe the hospital did make a mistake?