Mary was about 15 when she was betrothed to Joseph, so she gave birth to Jesus at age 15 or 16. Jesus was crucified when he was 33 or so, meaning Mary was about 48 or 49 by then. It is generally agreed that John wrote the Gospel of John c. 90 A.D. At that point, he wrote, “And NO MAN has ASCENDED up to heaven, but He that came down from heaven, even the Son of man which is in heaven” (John 3: 13). If one assumes that John did not mean that his use of “man” excluded women, then Mary would not have yet been assumed into heaven and would be at least 105 or 106 years old. Of course, maybe her assumption happened after that.
I’m not sure I follow your logic. John was quoting Jesus in that passage - words Jesus spoke around age 30, when Mary was in her mid-forties. They’re not John’s words. When the gospel of John was written is immaterial.
You are making a very common error trying to make the terms "Ascension" and "Assumption" synonymous, they ARE NOT.
Jesus Christ Ascended into Heaven on HIS OWN POWER.
The Blessed Virgin Mary was assumed into Heaven by her Son through HIS POWER.
Or maybe John was drawing a distinction between ascending and being assumed. It seems to me ascending implies power and assumption is passive.