It would be your church which made the switch, if you are correct.
Early Christians always used the metaphor ‘sleep’ for death.
This is why we say “rest in peace”. Falling asleep in the Lord is indeed death, and earlier generations of Roman Catholics certainly knew that.
The early church most certainly had an annual commemoration of her death, burial and resurrection. It began in the east, and was carried westward. This is why there are so many icons of saint Mary of Nazereth on a bier, surrounded by the Apostles.
goarch.org/special/listen_learn_share/dormition/resolveUid/ab076280b88253e1e0242ebd52c0f448
https://encrypted-tbn0.google.com/i...tc8XoAn5au7-FeOlVvcdRAH0N-cTs4WBuDAO9al9pRMr4
Note:
Jesus Christ stands back in the eternal space (denoted by the background) holding the soul of Mary. The soul is wrapped in what suggests both a winding sheet (for death) and a baby bunting (for a new birth).
The Feast of the Dormition began in the Jerusalem church, celebrated on August 15. It was borrowed into the western church in the eight century
on the same day. This is no accident, the tradition was imported to Rome in it’s entirety by a Pope Sergius I, and it was actually called the Dormition Feast in the west for many years!
As evidence that the tradition was extant in the west, one should not that there was an an abundance of artwork (usually commissioned for churches, sometimes above altars) entitled “Death of the Virgin”. This genre persisted for centuries, but the idea is now out of favor.
https://encrypted-tbn3.google.com/i...y2WrAwIA9XCTJYbjoqTMoEd3xF7Pg_uIElCN0N_1lAYTw
Caravaggio
https://encrypted-tbn0.google.com/i...kSZgEh0uNSLb2-kDoyHZnv0nKUEuaLt6Fmc5J3CEK09yY
**Cathedral of Strasbourg
https://encrypted-tbn3.google.com/i...tx6yzLhSsHHzKkqXxerZGCYZRsIOW6WII3byivdLLir**
Notre Dame cathedral, Paris
In the above Strasbourg sculpture, one can see Jesus holding her soul! In the Paris sculpture, one can see two angels about to lift her limp body up off the bier. The death, burial and assumption are
one fact, the details make a set. There is no other tradition, there are no other tales, the Pope couldn’t find any.
This is how the belief in the Assumption of Mary was held in the western (Roman) Catholic church. Some people like to think “well, that’s Orthodox, and we Catholics have a different tradition”.
When in fact there is no other tradition, there is only fidelity to it, or abandonment of it.
Do you think this vaguery is intentional?
Or are modern Roman Catholics reading too much into the vagueness? Is it wishful thinking at work here?
Inquiring minds want to know.

edit:
This is what EWTN has to say on the subject, I just found it, not expecting to see anything that agrees with me.