Perhaps we need to have a discussion of the Deposit of the Faith.
The Orthodox and Martin Luther believe/believed in the Assumption/Dormition of the Virgin Mary.
Martin Luther in his 1523 homily on the Feast of the Assumption:
There can be no doubt that the Virgin Mary is in
heaven. How it happened we do not know. And since the Holy Spirit has told us nothing about it, we can make of it no article of faith . . . It is enough to know that she lives in Christ.