I think it's more likely that those second-hand reports of what was said by detectives is simply misunderstood, just like the "squeaky clean" misunderstanding.
And again, I question the whole narrative about Serino really trying to go after Zimmerman. Absent some other source than "anonymous" ones speaking to ABC News, I'm not convinced. Especially since the charging document presented as SOP could easily be spun by the media as "going after" Zimmerman.
I am skeptical of the "misunderstanding" explanation, because the narrative is more complex than a mistaken attribution. Mistaken attribution is a very common error, easy one to make. But "walked up to the car, had such and so conversation, and window rolled up" is too much information to be a function of "bad hearing" (bad comprehension) on the part of Tracy.
"Squeaky clean" is a misattribution error. Serino was attributing that to Zimmerman; Tracy heard it attributed to the police department. But everybody agrees "squeaky clean" was said in reference to Zimmerman's record.
-- I question the whole narrative about Serino really trying to go after Zimmerman. --
He appears at an eyewitnesses house on March 5th - the woman whose child is the 13 year old dog-walking witness. This is what she said about that meeting:
[Serino] told me that he and the other officer with him felt that it was not self-defense and that they needed to prove it wasn't self-defense. And he said that I needed to read between the line because there was some stereotyping going on.... I took it to mean that he felt that George Zimmerman committed this crime based on whether it's stereotyping or racial profiling or whatever you want to call it. But those were his words. Stereotyping.
If all he's done is present the best case, and suggest or recommend it be no billed, why is he singing a different tune when speaking to the public?