Even though Piper equates "glorification" in the West with theosis in the East, I think there are differences that he does not elaborate on but probably could.
The EOC views it as a transformative process which comes by union/cooperation with God:
Theosis, or deification, is a transformative process whose aim is likeness to or union with God, as taught by the Eastern Orthodox Church and Eastern Catholic Churches. ... It is considered achievable only through a synergy (or cooperation) between human activity and God's uncreated energies (or operations).
Evangelicals however view glorification as removal of sin and the sin nature, and it is not a process but a future event. I will quote gotquestions because they usually reflect the view of a majority of evangelicals:
From
https://www.gotquestions.org/glorification.html
The short answer is that “glorification” is God's final removal of sin from the life of the saints (i.e., everyone who is saved) in the eternal state (Romans 8:18; 2 Corinthians 4:17). At Christ’s coming, the glory of God (Romans 5:2)—His honor, praise, majesty, and holiness—will be realized in us; instead of being mortals burdened with sin nature
As indicated by the gotquestions explanation of glorification, most evangelicals do not see glorification as the goal of salvation. They see the goal as to be "free from sin" and glorification is a way to achieve that.
What evangelicals and the EOC both share in common is that there will be a process of transformation. The disagreement lies in what is the purpose of that transformation (to be like God or to be free from a sin nature?), how it comes about (a life-long process of cooperation with God?, or a one-off future event?).