It's simple: it's your Workplace and your Data.
With Workplace, your data is owned by you. All Workplace do is keep your data safe, and respect your privacy for your peace of mind. You can Download Workplace from Meta's security guides to learn more about how your data is protected here:
Workplace has the highest certified security standards
The security foundation of Workplace is based on the highest industry standards, compliance and regulatory requirements. Their safety practices are regularly audited by independent third parties, so they stay ahead of the game when it comes to addressing constantly-evolving security challenges.