You don't need to deliberately create silos in order to secure a project. We've had people working on top secret projects and while people may not have known the specifics the company was kept up to date on the progress and outcomes of the project. We brought people in from other teams after an extra vetting process and additional NDA specific to that project.

Apple is great because their hardware and software is so well integrated.

If they compartmentalize their hardware and software departments, we might as well split them into a hardware and a software company.

Most companies aren't Apple.