I am not seeing any drop in traffic on our sites in this scenario....
I used the prebuilt Android segment, in conjunction with my own segment to exclude our mobile app. I didn't see any drop. So I took it a step farther and I added the prebuilt Chrome Browsers segment to see if there was a specific drop on Chrome.... still nothing showing for us...
Did you have any changes to your website, or to your tracking around that date?
Have you tested your tracking on Android mobile to see if you are experiencing any tracking issues there?
Have you checked with your SEO team to see if your website was hit by a potential Google Algorithm change that is making your mobile site come up less often in mobile search and discover traffic?