That certainly explains a lot. And isn't that surprising, considering...

"I don't know exactly what happened originally, but in the singularity you tried to save him by talking him into abandoning the Holy Grail War and leaving. The Doctor even pointed out after that making changes in the singularity wouldn't change what actually happened. But I never thought there was anything wrong with that."

It had meant making some detours that were probably not strictly necessary, but Ritsuka hadn't minded. Sometimes you just had to try your best rather than letting things happen in front of you.