More importantly: battery chemistry is weird and differs widely between technologies (for example, should you completely empty lithium ion batteries every now and then, or is that disastrous for the batteries? How is that for NiMh batteries? Does the memory effect exist? Etc.).

That overnight loss likely was (mostly) not a loss at all, but due to the difference in mileage you can get out of a warm vs a cold battery pack, or maybe even out of one that had recently seen small charge cycles due to regenerative braking vs one that hadn't (IMO unlikely, but as I said, battery chemistry is weird)

If Tesla told me that regenerative braking would improve available range in this situation, I think I would take them for their word.