Your interesting story attempted to answer an intriguing question posed in your title. Your analysis resonated well with me. I also read the longevity bottleneck hypothesis which gave me some perspectives but like you, I have my doubts. The good news is that the authors of the paper said "While the longevity bottleneck hypothesis may help explain observed differences in ageing between modern mammals and other taxa, there are other possible contributors for such differences. "

Thank you for writing this valuable piece.