"This is the day of the Holy Offering, which is wholly pure in soul and spirit. This is the day wherein the Queen, the mother of the King of Life, tasted death like every other human being, because she was flesh and blood."
Yes, it certainly appears Cyril held to some form of Marian doctine.
It also appears that the assumption was not part of what he believed.
Being Flesh and Blood and Dying does not nullify the Assumption.
Perhaps you need to read up on the Assumption