I consider this a bug in the Air 2s firmware and it has survived the two updates since its inception. I emplore DJI to fix this in the very next release:

In order to set the WB, I always click AUTO so it picks the correct WB and then switch to MANUAL with the intent to LOCK ithe WB value in. This always worked great and reliably with the Mavic 2 PRO or any of the prior drones I owned. With the Air 2s however the value displayed and locked in upon setting it to MANUAL is off (LOWER) by approximately 400-500 Kelvin. You can verify that easily by having the drone stationary setting WB to AUTO and then click auto off. You will see a difference in the picture on your monitor. The difference can be corrected by adding about 400-500 K to the "locked WB" value.

PLEASE fix this!

Hello there roamer105. I am sorry for the trouble this has caused and thank you for reaching out. I will cascade these information to the designated DJI department for further attention. Thank you.

Yes, also the calibration of White Balance in interval 5000K and 6000K is made wrong in FLY app....once you import the video in Premiere, you will see that you have deviations  (if you set it to 5600 on drone, the Premiere will say is 5100-5200....)....
For sure is a BUG (another one) from soft, they have not calibrated properly the software versus hardware.

agreed, this is very annoying