It always splits after you confirm the score board. However this raises one issue:

The final split won't occur right after killing the final boss. Instead you'll have to confirm the final score board to trigger the last split.

Would it be possible to change the rules to accommodate for this? It would make the run 3 ish seconds longer and we'd probably need to adjust the current times on the board though.

Can I still use the auto splitter even if the rules won't be changed? I could just read the time on final hit from the video.