Here's a great piece on the concept of mining that will put into perspective the "why" of what he is clarifying:

https://open.spotify.com/episode/4A398lNlGr7qWAvx6XRaiu?si=575a4f6cf89c40ba

But what he is saying is true. Mining is essential to bitcoin, with or without new bitcoin being created. Nodes validate the information and blocks coming in and then pass them on, but a normal node of a user isn't mining. The only way to make a valid block is to validate all the transactions, and then add the proof of work hash.

In short:

all nodes maintain the chain, only mining nodes add to the chain