I think the differentiator is that some people can and do remain effective at a primary task while handling a multitude of distractions, and that this trait strongly indicates high ability overall.
You're not entirely focused if you're answering emails on your phone.
Maybe Greg's 50% focus is still good enough for answering to Altman and doing other stuff? It's still giving 50% to both or a different mix.
It's also disrespectful if you're with other people imho.
Anyway my main point is that if you're expecting people to answer you urgently, don't write them an email but find a better channel.
Apple has context-specific notifications and manual DnD exception list.
Short iOS email VIP list can be manually curated.
Interrupt-automation exists to support a spectrum of human priorities and workflows.
Eg you’d expect a CEO to enter a meeting, receive a variety of reports from their staff and make a final call or two — and then moving onto another meeting in an entirely different domain — and do so fluidly without interruption.
Which would make it a lot easier to be readily available for ad-how things like emails. Though 5-minutes feels a little much.
If you can answer every mail in minutes from important people, then how can you meaningfully do other stuff?
It's perfectly fine to spend a day without answering to the head of YC if you've had the entire day full at hiring, talking to investors, etc. You can't do that effectively and be distracted by your phone all time.
This is about the nature of emails themselves, if they conveyed a more urgent information then a phone call would've been better.