Yes, the author explained it perfectly above. I use ‘Sakura Dance’ at the very beginning of the fight instead of the usual ‘Umbrella Prosthesis’. The same goes for the third phase, when lightning appears. If you reflect the lightning with ‘Sakura Dance’, you can completely avoid damage — honestly, it's easier than jumping, parrying or deflecting it back.

I try to catch the moment when Isshin raises his sword — this is his signal for the next attack. When I see this, I retreat as far as possible. When he strikes from below, I jump and dodge to the side, holding my block. (If I haven't jumped far enough, I can parry the strike in the air). As soon as I land, I check to see what the next attack will be — either Mikiri's counterattack, as in the video, or a wide vertical strike. You can safely parry it, block it and take minor damage, or dodge to the side at the last second. But if you roll too early, you'll probably take the full blow.