I understand that, but all of that boils down to "trust the bureaucratic system".
It's inherently problematic that the justifications for animal research trials are not required to be publicly posted. If the justification is legitimate, you should feel comfortable defending it publicly.
Keeping it secret and gatekept to the scientists in the field means that the broader public has no real input or say on topics that are not just purely scientific, but deeply moral and ethical.
Virtually every scientist I've ever known has been a deeply moral person, but at a broader scale, there have been enough scientific studies that have been used to abuse people and animals, that their shouldn't be a culture of 'trust us scientists, we always know what the right thing is'. There should be a culture of open transparency and verification.