all primals have been summoned in the past, this article is talking about years ago the primals were summoned and defeated then resummoned, not currently. We dont need to worry about them at the moment because currently they are in slumber where ever they are in primal heaven ready to be summoned again.

eight summers past
A handful of years ago

edit for Nakiamiie post: There have been talks about the other primals in other quests before, so its not like they arent fearful of them coming back.