Salaam,
A
possible explanation is that
the people of Noah used a different calendar system and that
Noah and his people lived a "normal human life span".
"1000
sanatin illa 50
ʿāman", could refer to "Noah's age at the time of the flood" according to their calendar counting system and not to an exceptional longevity.
28:14 And verily we sent Noah (as Our messenger) unto his folk, and he continued with them for a thousand years save fifty years; and the flood engulfed them, for they were wrong-doers.
https://en.wikipedia.org/wiki/Sumerian_King_List... "The antediluvian reigns were measured in Sumerian numerical units known as sars (units of 3,600), ners (units of 600), and sosses (units of 60)."...
Mohamad Shahrour
https://youtu.be/5dCOalhMZtk(in Arabic)
والله اعلم
Allah knows best.