How “old” was Adam when he first met Eve?
I understand your point, but none of us were there.
One thing I find fascinating about all this is that the dinosouars could not have lived for more than a few days in our current world. Their bone and muscle structure could not have supported their weight unless they were all neck deep in water and the flying creatures could not have flown, other than maybe some crude gliding. They were too heavy.
So we don’t know yet what was going on. We can only speculate.
There is an exciting new theory about early Earth. Rather than having a liquid metal core, the Earth has a liquid water-based core. And the Earth was much smaller in diameter back then, with a non-watery crustal surface. As the core heated, the liquid water core released steam which broke through the crustal surface and created rifts which drove the continents apart, and spurting water from below created the oceans. Gravity was lesser than now when the dinosaurs roamed the Earth, calculations taking into account a different core than now. The Earth expanded like a balloon over millions of years, and gravity increased to what it is now. These theories came about due to experiments on rotating droplets of water done by astronauts in space. Non-liquid particles move to the outside surface while the water stays in the core, the water heats and hot steam bubbles remain in the core, expanding the droplet.
As you say, we can only speculate. But scientists always get whiplash when new evidence makes them toss out their old theories that were thought to be "facts". They still don't truly know what happened.