Long answer to your short question...
G&C are in right-to-left mode, IMHO. Its all a means to an end. Consider the stakes from their point of view...
They know they've lost Caylee, and anything they do to admit Caylee's dead would only serve to remove the single remaining means they have to distract the press, and, ultimately, plant a reasonable doubt in the minds of the jury. They have a single objective now, IMHO. They must continue to pump the sightings out for the defense to be able to go into court and say, "Casey was framed by LE so the state atty can close a high-visiblity, politically important, case they otherwise couldn't solve. They can't find the body. They don't know what happened. They can't prove Caylee died at Casey's hand."
If the defense capitulates to "Caylee's dead", then, the jury will be able to focus solely on who did it. If they focus only on who did it, then, Casey will have no defense on why she didn't come forward on her own immediately, except to say she was convinced by ZFG that Caylee was still alive. Casey will not be able to provide ANY proof of how ZFG convinced her of this...no phone calls, no texts, no witnesses, no prior contact, no handwritten letters, no emails, nothing. With Casey's history of lies well documented, the case stacked on Casey-did-it vs. ZFG-did-it is so overwhelming the defense needs the "Caylee's alive" reasonable doubt card more than desperately.
Soooo...ANYTHING G&C can do to support that the relationship between them & Casey during the 6/15-7/15 period wasn't strained, was normal, was no cause for concern, is their effort to paint Casey as the martyr...putting on her best effort to protect Casey and the family from the horror ZFG threatened. They have no other alternative from their vantage point...anything else is to support Casey's conviction. If G&C paint Casey as being deceptive to them in any way they just play into the truth that LE knows, the prosecution knows and the jury will certainly determine was a result of Casey's motive to hide the crime.
Specific to the chase. Cindy knew immediately that a chase would be counterproductive for the defense and, besides, she knew her 4Runner never went missing, hey, Casey was in Tampa tending to ZFG, or up in Jacksonville with Jeff (she couldn't be at the house borrowing my car or my whole story's busted). Right? Right! Good, end of story...never happened. George, on the other hand, knew he saw Casey from a distance in a dark SUV leaving the house. Perhaps he'd told this story to others besides Cindy and knew it would surface to LE eventually if he didn't tell it. It took George a little longer to get in right-to-left mode...recall he initially broke out on his own to the FBI w/ the chase info...but later in his statements he started indicating that it was common for Casey to borrow Cindy's 4Runner, etc. and eventually, has to force the story to work w/ a non-threatening-Casey-just-borrowed Cindy's car story. Recall how George's gas can story morphed from the witnessed, 'Here are your effin' cans' to the cordial 'I reached in and got them'. George saw enough to convince himself he was chasing Casey...the details (e.g. 4Runner, Panda sticker, Pontiac at the house) were filled in by either by his subconscious, in a conscious effort at some point to fall in line w/ the defense strategy, or some combination of both.
G&C are locked in a lose-lose battle, they know it...and they're playing their hand as they feel they must. Their choice to make.
Poor Caylee