User blog comment:Kaido King of the Beasts/Chapter 896: After Beating the Mochi, Pop into the Oven/@comment-24850639-20180302165349/@comment-207.164.16.130-20180302192816

As for the ending between Luffy and Katakuri, I may be wrong, but the panels give me the impressions that they both stop their attack just before hitting as a demonstration that they would have the upper hand. It's a common trope between two character that tries to intimidate the other or show their superiority over someone. The results being that both Luffy and Katakuri aknowledge each other as worthy opponent. Then then both fall from exhaustion. The floor colapsing being an after effect of the massive shockwave created by the momentum of Katakuri's attack stopped mid air. Yet again, I may be completely wrong :D