"History is written by the victors."
True and often, the victors co-opt the popular myths of the conquered, and the myths evolve as the prevailing cultures change. It's a two-way street. The principal did tell a story about Reid at the funeral that was kind of true but had some mistaken details. I don't know if this story will think too deeply about it, but it would be interesting.
Here's a possible scenario- Vegalta wins the war, and needs to rule over the conquered Altein people. The Altein government was corrupt and the common people were starving. To win them over, Vegalta improves infrastructure and gives them food. They take the story of the hero Reid and rebrand him as a good person who fought for the commoners and despised the nobles. Reid fell in love with Elria and when she died, he visited her funeral to swear to fight for Vegalta and help save the people of Altein. It's a nice unifying myth that within a few generations could become historical truth.