Why does owning the source code decide whether the platform outlives the grant?
Every engagement ships the full repository: application code, custom modules, theme, build tooling and deployment configuration. It runs on your servers, your cloud account, or ours, and the choice is reversible. Another team can pick it up, because Drupal coding standards, automated test coverage on the code we ship and documentation written for a developer who has never met us are deliverables rather than extras.
For a commercial client that is good practice. For an organisation whose funding is renewed in cycles it is the difference between a platform and a liability: when the programme that paid for the build ends, the successor programme can take the same codebase to whoever it likes, including an in-region developer, which is usually cheaper and is often a donor preference. The full argument is on why you own what we build.