Pre/Post-Flood -- THAT is the key.
The entire world was re-booted. The planet itself, magnetic field, air pressure, genetics, and perhaps shield from radiation were dramatically altered.
Pre-flood fossil record reveal much larger flora and fauna, indicating a longer genetic "expiration date." Some argue that today's current "dating" methods and mechanisms don't apply since the earth was "re-booted."
If that explanation were true we would be finding the skeletons of pre flood humans that are super old.
That is not the case. Just the opposite is true. Ancient skeletons are almost always fairly young which indicates a short life span.
I think if we accept the listed ages as accurate, that you give the best explanation.
The planet, the atmosphere, etc. changed over time. They lived in a different planet than we did.