Even in an authoritarian country answering to Hell, it's not easy to prevent rumors, at their tech level and social level. There are too many people, especially in the Imperial Palace, with enough self-considered impunity that they'd whisper a few words among each other, or ask questions of another. Security may stamp out rumors elsewhere, but they've got to be able to exchange whispered rumors among themselves to do their job correctly; or at least, that's what Security wizards sure seem to think. Or Asmodean nobles. Or priests of Asmodeus. They're members of the Inner Ring, and privileged to be the ones who trade rumors if they want, while stamping down hard on all loose talk among the Outers who don't need to think, just be told.
And Cheliax doesn't think about informational security the same way dath ilan does. They don't have an explicit concept of information theory and probabilistic entanglement and improbable observations narrowing down probable worlds. If a top-secret Civilization project requests two hundred mice, and most other projects don't do that, then the mouse order is also obviously top secret, period, your job isn't to figure out what an adversary could deduce from a piece of unusual information but to deny your adversaries as much information as possible. Even if you're at +3sd they may perhaps be at +5sd, and you won't see all the connections that they'll see.
Dath ilani children's fiction is replete with cautionary tales of fools who assumed that some fact could not possibly be deduced from the scanty, unreliable information that some slightly less foolish person possessed. Adults, of course, read about more sophisticated and plausible errors than that.
Not that every dath ilani has the deep information-theoretic security mindset either, to be clear. Any real information-theoretic-security expert of dath ilan - as opposed to some random punk kid on an airplane - would've told Keltham, during the Nidal attack on the villa, that as soon as his life was no longer in immediate danger, he needed to get the shit out of those Obviously Strange Clothes before he went into the villa and anyone project-uncleared got a close or extended look at him. No, not because an ideal agent could use a mere glance at the zipper to deduce precise manufacturing technology not currently known to Golarion. Because the clothes are incredibly abnormal and therefore a highly improbable rare signal and therefore represent a potentially massive update for any adversary who is smarter than you and making unknown deductions; seriously what the shit is Keltham thinking.
A dath ilani proverb runs, "The most important part of any secret is the meta-secret that the secret exists." (Not literally always true, of course, e.g., consider public-key cryptography.) Cheliax has this concept deeply and instinctively for private interactions, hiding the very existence of secrets from adversaries who'd want to pry them out of you. It doesn't think in quite the same way about most secret government projects, unless there's a specific and obvious reason why a secret also needs to be meta-secret. Tyrannies are not based on a deep respect and worry for what your lessers could do with the information they have, if they were secretly master criminals opposed to you. In an Asmodean tyranny, if you order someone not to think about something or ask any further questions, they don't ask any further questions and make a sincere try not to think about it. That, and not hiding the very existence of the secret itself from anyone, is the first line of defense around secret government projects in Cheliax.
So if a top-secret Chelish project asks for a budget estimate on two hundred mice, the project manager will think about whether they believe anything top-secret seems obviously deducible from the mouse request; and if there's an obvious way to deduce something genuinely ultra-top-secret, they'll mark the mouse order as being also genuinely ultra-top-secret. Otherwise, it will soon be widely rumored within the Inner Ring - this being something that would make dath ilani informational security experts spit out their drinks - that a top-secret Chelish project ordered two hundred mice, no, nobody's allowed to ask for what. When Abrogail Thrune issues an order, it's put forth under Crown authority so everybody knows how important it is and what happens to them if they fuck up; rather than being issued anonymously with a quantitative priority that isn't any higher than it has to be to get that job done, rounded up to make the exact quantity less revealing.
Even Hell thinks that it's fine for random contract devils in Dis to know everything their owned souls know; they won't repeat it, right, who cares if their behavior changes in externally observable ways given their knowledge. Hell is playing their informational security game against mortals in Golarion, not gods or dath ilani.