This makes a lot of sense. I was riding bikes in traffic before I could drive a car, so I have always driven like a cyclist - a lot of awareness, the assumption that you are usually invisible, the expectation that someone probably will turn in front of you/fail to stop etc. It's saved countless potential accidents.
In a peloton it may be less complicated than how much information the brain can process. i.e. could it be less about processing inputs and more about maintaining a consistent sense of awareness.
An analogy: when you're walking in a busy city, everyone walks in a kind of flow. Then there is someone who is texting - they step out of that flow, by failing to maintain that basic level of simple awareness. And it's super obvious to everyone else, and a bit annoying.