In either case, someone needs to have moderate expertise in multiple areas of tech. If it's wrapped up in one person, the business needs backups to deal with the bus factor. If it's spread across multiple people, you now need to be selecting for people with moderate tech expertise AND the ability to communicate and work together with other people effectively. And you need someone to manage their process (in some manner - doesn't necessarily mean micromanaging).

So the 'full-stack rockstar', if they have good communication skills, can exist and be valuable, but still isn't the best long term solution for a business of any size.