No. There are two different things, Secure Boot (which prevents the device from running unsigned software) and Trusted Boot (where the device can run anything but can prove to a remote party that it's running a specific software).

Because this would only leak private keys inside the device, you can only attack Trusted Boot (where producing trusted signatures is important), not Secure Boot (which only verifies signatures that were produced elsewhere).

If I’m reading this correctly, it means the private key of a certificate is leaked during generation. Boot chains rely on the verification of certificates and signed data, not signing. So no.