2020.12.6 is the public release of 2020.12.5.7 with stop light and stop sign stopping. Presumably 2020.12.10 was from a different branch, I think these version numbers are just automatically created by Tesla's system.
I updated to 2020.12.6 and did a test drive. It won't go 5 over while on autopilot, just the speed limit. It notifies you 500 feet from a red light that it is slowing then stops very comfortably. When the light turns green, it doesn't start on it's own, but goes when you touch the accelerator or cruise knob.