Yes, but the point of binary transparency is to assure device owners that their devices are running official Google firmware, even if Google’s signing key is compromised or if a court orders Google to sign a malicious image.
A verified boot chain does not provide this assurance.
That’s a slightly different issue. Right now, Google could push a customized malicious firmware just to you. No one else would have a copy, and no one would be able to reverse engineer it to detect that it’s malicious.
With a fully functioning binary transparency system, Google would have to publish the fingerprint of the malicious firmware. An even stronger system would require that they publish the entire image as well. Then the attack could be detected.
A verified boot chain does not provide this assurance.