I’ve seen one theory that it might be something to do with not needing as much chewing and how quickly you can eat it. I can’t remember exactly the article I was reading but apparently there is a massive difference (e.g. insulin spike, etc.) eating apple purée of one apple vs. eating an apple.

Needing to chew less processed food may help just by being kind of rate-limiting (slowing down how fast you can get the food in), but also the enzymes in your saliva have time to start working on the food before you swallow it.

If I recall correctly I have also read (perhaps the same article, but maybe somewhere else) that some processes related to digestion might be triggered when you start eating (chewing), so the fact that you can eat so many calories so quickly before those processes get going might make a big difference too.