(IMO) It wasn't just throw 40k into an unlocked car, it was put it into the red car in the garage. JW had been given access to the garage either with a remote or he had the remote combination programmed into his BMW. He placed the money in a manilla envelope and closed the garage door. The money was securely delivered by JW as instructed. This may also have been JW's motivation for lying because he was covering himself for how he delivered the money as he was being grilled by police.
Figure of speech "throw cash in the car." Yes, possible JW had no reason to have any qualms about delivering as per instructions. He assumed SS would retrieve the cash immediately since he phoned ahead and messaged after he carefully put the "package" in the driver's seat and locked the garage.
As you suggest, JW could have felt the need to protect himself from unfair accusations down the line or a complaint about how he had delivered the cash. He doesn't know if investigators are setting a trap for him, what they might be driving at, why these details seem significant to them.
I'm leaning now toward an innocent explanation for JW altering his account including the possibility that LE's grilling itself led him to be flustered or confused.
The more I learn about how this horrendous crime went down, the more I find surprising that anyone who knew DW would ever enter into collaboration with him, trust him to accomplish anything but senseless mayhem. I'm now leaning towards SS coming up with the 40 k "plan" in an effort to buy time, hoping a reward in sight would induce Wint to keep them alive longer until he got his hands on it, and in the meantime someone would realize business not as usual and raise he alarm.
Any accomplices could be as deranged, out of control, and maniacal as Wint. Deluded too to think they'd find untold riches stashed in a home safe or that SS could raise millions with an hour's notice.
And the getaway arrangement was a study in reckless stupidity.
There's buzz here and other places about a grand jury convening and Wint's relatives being called on.
Any one know? I missed the details and did not note a source.