Note: Jade is a fully offline, cold storage device and your wallet (or seed phrase) never leaves your hardware wallet. Even if your oracle is unavailable, you can still access your funds using Jade and your recovery phrase. To learn more about Jade's security model, click here.
Secure elements are closed-source chips that are integrated into hardware wallets in order to protect them from physical attacks. They are typically covered by NDAs, increase the cost of the hardware wallet, and prevent users from building their own device.
Instead of a secure element, Blockstream Jade uses a unique security model that allows it to remain fully open-source while also being protected from physical attacks and achieving similar (if not better) security from this potential threat - by acting as a "virtual" secure element.
The blind oracle model that Jade uses is fully open source, and is truly blind. It knows nothing about Jade wallet data, and doesn't even know the user's actual PIN. Users may use Blockstream's blind oracle to protect their wallet, or they may run their own.