I was about to report this same problem but for MOONSTONE, I'm currently running stable
xiaomi.eu_multi_MOONSTONE_V14.0.6.0.TMPMIXM_v14-13.zip
Whenever an app is downloading something, the icon inside the notification shade will flicker when the notification is not expanded, also the notification icons in the status bar are in full color, I too have selected "Android" and not "MIUI" for the notification shade style, I believe they should be monochrome.
Update: I found out the full color notification icons can be turned off here:
Settings >Notifications and control center> status bar > use app icons for notifications.
Disabling that toggle will bring back the monochrome icons native to the "Android" style notification shade and will also resolve the flickering.