After release, a game can receive bug reports, device compatibility problems, content requests, and store notices. Without an agreed support process, every message can feel urgent and nobody may know who can approve a change.
A game that runs on a device is not yet a complete store release. The project may also need account ownership, signing, listing material, content information, privacy details, testing access, and a plan for review feedback. Requirements vary by platform and change over time.
A source folder is useful only if the next person can understand and build it. Game projects may depend on an engine version, plugins, imported assets, export settings, and platform-specific tools. Those dependencies should be part of the handover.