I am immensely curious how a constant current is maintained without feedback.
No magic required.
Any constant current regulator does have and uses current feedback internal in it's own circuitry, so it does indeed know what the current is at any specific time and if the load resistance changes causing a change of current the regulator will raise or lower the loop voltage to keep the current at the desired constant current value desired. That part is standard for any charger that uses a constant current charging method. What the OP was asking is how to detect when to stop charging using the -deltaV detection method, which I think I answered satisfactory according to the OP's last posting?