Startup studio
The idea of Studio is that it's an organization that acts as co-founders for startups. They have resources to streamline the creation of the early products, they know how to validate ideas, and have a network to achieve speed faster than what a single founder could.
Nascent Ventures, for example, could have been a studio, but they created companies from the onset and didn't share any kind of resources.
Once ideas have been tested and validated, the studio creates a startup as an independent organization. The business model for studios can be associated with keeping equity on future companies (carry), as well as charging management fees for the services provided.
Advantage of studios
I believe the largest advantage is the compounding effect. If ideas don't pan out, the knowledge can stay in-house instead of lost as what happens when startups close.
The knowledge also accumulates over time, for example the network of early adopters, access to funding, and related skills that a single entrepreneur may lack (especially if it's their first experience).