There is no expectation that the police have to be truthful to a suspect. All that matters is that the motive on the part of the suspect was to commit a crime even if there was no actual set of circumstances where a crime could be committed.
No, there isn't an expectation, but then again, it's simply another reason not to trust law enforcement overall, in general, period. They can lie to you and call it police work, but if you do it to them, it's a crime. I'm a law abiding citizen, but I don't trust law enforcement one iota and I don't give a shit if you or them want me to believe that they have my interests at heart. They demonstrate daily they don't and never will. I'm not going to go out of my way to antagonize them, but I certainly won't be Mr. Cooperative if I don't have to be with them either.