The latin is that one becomes so close to God that one eventually is in union with God, essentially becoming, after the rapture, part of God. not that one becomes a god. The byzantine Theosis is that one ever become more like God, but never becomes part of God, per se.
That one becomes a god is a heresy.
That one becomes part of God is a theologumenon that can be VERY divisive, but isn’t itself heresy.
That one becomes united to God is a latin theologumenon, but is not itself doctrinal, tho’ neither theosis as fully expressed in Byzantine literature nor enfoldment into the rapture of union to God is counter to the doctrinal belief in becoming ever closer to God.
By their very nature, all theolgumenia are potentially divisive when mistaken for, or promoted to, doctrine and/or dogma.
In both latin, and from what I’ve seen, coptic, theology, the emphasis is on the divine presence changing the faithful to be more like God.
In byzantine, the emphasis is on the opening one’s self up to the grace which God made available, and letting it work, healing the division caused by the fall.