it's a useful distinction IMO (and IIRC, SCP didn't come up with it)
infohazards are a chronic risk (the state of knowing is the danger) whereas cognitohazards are acute (the act of perceiving is the danger)
if u survive a cognitohazard, recalling it isn't dangerous. after u know an infohazard the only way to be safe again is to Un-Know It
(which in fairness SCP's canon makes kinda trivial in most non-lethal cases--)