Mac OS Catalina, uneven battery drain in AirPods

I have noticed something about my AirPods, and I want you to help me understand if this problem is due to AirPods or Mac OS.

Initially, my AirPods were charged to 100%. But After a few hours of usage, I noticed that the left one was at 27% and the right one was at 9%, this got me wondering what causes it, because it's a brand new pair of AirPods.

So, I went into Settings -> Bluetooth -> AirPods (clicked the "Options" button) here:

that brought me to this screen:

The "Microphone:" setting has 3 options:

I noticed that when I set it to "Automatically Switch AirPods", it only uses the right AirPod's microphone, I checked it by going into the Sounds settings here:

and then when I tapped on my left AirPod, the "Input level:" bar didn't budge, and it only moved, when I tapped on the right AirPod.

Could someone with AirPods and a Mac do the same test and confirm this for me? I'm trying to understand if going to Apple to fix this problem is going to be a waste of time for me or not, this could be a Mac OS issue after all.

I noticed last night that my left pod drains faster than my right, and doing your test just now, I can see that (with Automatically Switch AirPods selected) my left pod microphone shows input volume but my right does not.

Update: I have found that my AirPods (2nd Gen) are evenly charged with left and right double-tap turned off, and sound input set to internal microphone. I suspect that selecting AirPods for input source was the main issue.