I'm not sure if I'm understanding correctly.
Animals succumb when their brain ceases to function, a result of either a direct hit to the central nervous system or significant blood loss.
A bullet that fragments upon impact maximizes internal damage rather than exiting intact. This fragmentation causes extensive tissue damage.
If a bullet exits, it suggests that not all of its potential for causing internal damage was utilized.
The fragmentation of a bullet, particularly in vital areas like the lungs, can incapacitate an animal quickly by disrupting its blood circulation, eliminating the need for tracking. The optimal outcome is achieved by causing the maximum possible trauma, with bullets designed to exit being less effective in this regard.
The effectiveness of copper bullets, or other types, in causing lethal outcomes isn't in question; rather, their mechanisms of interaction with soft tissue differ. Opting for such ammunition, whether for personal preferences or compliance with regulations like lead-free mandates, is entirely respectable and beyond critique.
For what it's worth, I used to run Partitions and Accubonds. Once I learned about the science of wounds and trauma, it became tough to not question what I "learned" before. This was a good read
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6208714/ And there's lots more sources about temporary and permanent wound cavities etc.
As the saying goes "Run what you brung." But lots has changed in the hunting world in the last 6 years too.