Can't be particularly good sources if they have left you with the impression the areas concerned were merely crevices in a coral reef rather than a limestone cave system - and saying you have "a number of sources" for insisting it is still a complete mystery is roughly worth
nothing if you don't actually provide them.
Incidentally, I rooted out
the relevant clip from the documentary you mention..... it actually says explicitly that the turtles died in a complex system of caves, so you
really didn't pay that much attention

as for the eggs, the clip shows that they are within the body cavities of the turtle skeletons.... so they are pretty clearly the remnants of eggs which were held within the turtles when they died.
And there I was thinking your introductory statement said this was a thread for
"substantially informational" content