[None of them know just how true it is. If it hadn't been for Reis, the warrior would likely have become a warrior of Chaos doing nothing more than obeying Garland's will.]

Indeed. As long as they are now fully devoted to upholding the light, then having been drawn to Chaos's side in the past matters little.

And even if they cannot remember fighting alongside you, it does not change that you are a comrade.