It may be in the future, but for now it is no different from Fedora Workstation in terms of security. Please correct me if I am wrong. AFAIK Silverblue has no additional sandboxing or any other improvements to security.
Fedora is notable because any software installed via repositories has a policy written for it, so it is already far more in effect than you might realize.
It's entirely comparable to Android sandboxing because it's part of the foundation of Android sandboxing.