Keeping the same 10,893 detections before and after correction makes the calibration improvement interpretable. There is an important population boundary in the threshold table: these detections were selected using original scores of at least 0.25, so a corrected-score threshold is being evaluated inside that already-filtered set.
If deployment applies Platt correction to lower original scores and admits some of them, the 1.31-point ECE does not yet validate that expanded population. I would report the original-score floor alongside each operational threshold, or repeat calibration evaluation over the actual deployed candidate set. That preserves the distinction between remapping existing detections and changing which detections reach users.