I wanted to see if there was a correlation between the baal wave spawn animation and the timing of re-entering the throne room, so I put these two clips side by side. I also think it might be useful to note more precise timings for things so I added a timer.

Maybe some science can be done using this information. Sorry for the scuffed start of the skip clip, you can still hear they are within a frame of being in sync by the two ice blasts that kill the final mob.

Edit: I've only included one in the video, but I tested three different successful skips and the timings of re-entering throne and the start of the wave spawn animation were virtually identical. 3 is not a large sample size but y'know.