CLion static analyzer highlighted the potential mismatch in argument passing order. Look at this call chain:

void G1AdaptiveIHOPControl::send_trace_event(G1NewTracer* tracer) {
  ...
  tracer->report_adaptive_ihop_statistics(get_conc_mark_start_threshold(),
                                          actual_target_threshold(),
                                          G1CollectedHeap::heap()->used(),
                                          _last_unrestrained_young_size,
                                          ...);
}

void G1NewTracer::report_adaptive_ihop_statistics(size_t threshold,
                                                  size_t internal_target_occupancy,
                                                  size_t current_occupancy,
                                                  size_t additional_buffer_size,
                                                  ...) {
  send_adaptive_ihop_statistics(threshold,
                                internal_target_occupancy,
                                additional_buffer_size, // SWAPPED HERE
                                current_occupancy, // SWAPPED HERE
                                ...);
}

void G1NewTracer::send_adaptive_ihop_statistics(size_t threshold,
                                                size_t internal_target_occupancy,
                                                size_t current_occupancy,
                                                size_t additional_buffer_size,
                                                ...) {
  ...
    evt.set_currentOccupancy(current_occupancy);
    evt.set_additionalBufferSize(additional_buffer_size);
  ...
}

I think current_occupancy and additional_buffer_size were swapped accidentally in G1NewTracer::report_adaptive_ihop_statistics.

I have not looked at the actual JFR event dump, only to the code inspection.