The Eastern Churches both Orthodox and Catholic believe in purification but what we do not agree with the West is the need to make expiation for sin after death (Purgatory). We believe that a) the souls of the departed require purification before entering the Kingdom of God, and b) that prayers for the dead are efficacious to that effect.
I’m sure the filioque is a non-issue for most Orthodox. Just the ones you find on FaceBook lol!
There are two levels of theology; theologia prima and theologia secunda. The first is the foundational belief of the Church, as embedded in its rule of prayer. Where we differ, and this may be where the author refers to as terminology, would be the theologia secunda. Theologia secunda is the result of contemplation and reflection upon theologia prima. Because doctrine is culturally, historically and linguistically conditioned, it is this experience which shapes how the East and the West understand the theologia prima.
I think Purgatory is a good example of this. At theologia prima, we believe in the need for purification after death. Purgatory represents the theologia secunda of the Latin Church, and it is their prerogative to develop doctrine as they see fit.