I've noticed the same issue for probably a couple months now on my 3.6L SE. Took it to the dealer finally and they told the pressure held at 1.5 BAR. So, I told them that coolant is like AC refrigerant and is not consumed. If the level diminishes, there is a leak.
I teach high school auto shop after over 15 years in the heavy truck fleet maintenance and am double ASE master certified (auto and med/heavy truck). Let me just tell everyone here that coolant does not dissipate or evaporate. If you look in any owner's manual in the last decade or two, you'll likely find in the maintenance schedule a coolant replacement interval of somewhere in the 100,000 mile range. If your dealer tells you some nonsense because they don't know what's going on with these super slow Atlas leaks, just point out that the owner's manual does not even have a replacement mileage (and our manual maintenance schedule goes up to 150,000 miles).
If anyone gets this figured out, let us know! My super slow leak took a couple months to trigger the low coolant warning.