History geek pups are awesome.

I think the same applies to Albus!

There are so many different versions of what happened (people trying to forget, so they gloss over things; other people remember things terribly vividly but possibly not wholly accurate, etc. etc. etc.) in the Great War, that he could never get a straight, consistent story. All he knows for sure is that Bad Stuff happened, and it took some time to rebuild their society afterward.