He's not reality bending. He for now has 4 abilities:
(Partial-)Gigantification, body adaptation, that heartbeat regeneration thing and the ability to make objects/living things rubbery.
He's therefore also not phasing through anything.
When he punched Kaido's head in, you cannot see the outlines of his knuckles on his fist anymore and afterwards his fist is drawn in armament, while that same CoA wasn't seen during the actual attack, which means that his fist was covered by the backside of Kaido's face then.
Btw you can see it much better on the page before the one that was posted here.
Also notice that it was a CoC infused punch, so that ability on itself might not even be harmful, only unpleasant to experience.
Reality bending is a completely different animal, he's not doing things like the mask or Genie from Aladdin
Absurd things Luffy did
- making ground able to reflect a blast
- increasing his muscle mass freely, either by hypertrophy (enlarging his own muscle cells) or generating new rubber muscles cells or protein. Either way rubber absolutely cant do this, it's creating solid component of the cells instead of simple ballooning
- didnt care even when being eaten or inside a digestive tract (acid, proteolytic enzymes, fire-generating organs etc) of a dragon and get no damage while still able to ricochet and hit Kaidou from the inside
- rubberizing Kaidou's eyes as a glove to grab Kaidou's nose to escape from Kaidou's mouth
- shrugging of biggest blast breath without any explanation, without any damage, without any care
- running on air with road runner physics without elastic principle
- get practically no damage from Kaidou skysplitter CoC attacks, when those are attacks that are able to split and destroy islands since Hakai which has island AoE came from non-serious Kaidou who used no CoC at all, while Kaidou is currently serious and us using CoC. Rubber should have limits but Luffy's body currently have none.
- emphasize the limitless durability by saying that he's having the time of his life.
