Version: 55.0.2883.29
OS: Chrome OS

My setup is like this (somewhat non-default):
Chrome OS device 1 (samus):
2 accounts (@google.com and @gmail.com)
multi-profile sign in enabled
Chrome OS @google.com account has Android apps enabled
In Android settings (accessible when I sign in my @google.com account on this device) I am signed into @gmail.com account as my primary account

Chrome OS device 2 (minnie)
Many accounts, one of them my @gmail.com account
Android apps not enabled (sign-in flow not started).

Now the steps:
1. On device 2 sign in @gmail.com account
2. Change UI language in chrome://settings to RU
3. Sign out of device 2
4. On device 1 sign in @google.com account
5. Open an Android app

What is the expected output?
App displayed in the system UI language of device 1 (EN)

What do you see instead?
App (all Android apps) displayed in RU

To revert this language change I did this:
Signed in device 2 again and changed the system UI language.

Note: interestingly enough changing language setting on device 1 (the one with both accounts) by signing into @gmail.com and switching to RU did not affect Android apps on the same device when signed into @google.com account. It is all quite confusing although I am not sure how many users would be affected by something like that.

Note: Since changing the UI language from Android settings on Chrome OS is disabled this whole flow felt as if I have locked the room and threw away the key (I had to find the same device where I changed the UI language to get the Android language back).