Would certainly recommend taking advantage of the 7 day free trial of Wrestle Universe to check that one out. They do have English commentary.
Not sure it was ever mentioned, but Alexa, the former Sasha, said that they did it because Chono, Muto, and Hashimoto were all going to retire at the same time and have a three way match, but sadly Hashimoto passed away, and this was them honoring that pact or wish you can say that they made.There was absolutely no reason for Mutoh to do that other than letting Chono share in his own retirement moment
Holy shit maybe to New Japan for him?