Steps to reproduce:
0) Add a child account to the device and clear app data
1) Go through the FRE until the sign-in confirmation screen
2) On the sign-in confirmation screen, tap on the the "Settings" link in "You and your parents can manage Chrome Sync and personalization in Settings". 

Expected:
The account settings fragment should open.

Actual:
The FRE finishes without showing account settings.

The problem seems to be that forced signin marks the FRE as complete (https://cs.chromium.org/chromium/src/chrome/android/java/src/org/chromium/chrome/browser/firstrun/FirstRunFlowSequencer.java?rcl=11601c08e92732d2883af2057c41c17cba890844&l=207), which makes FirstRunSigninProcessor return early (https://cs.chromium.org/chromium/src/chrome/android/java/src/org/chromium/chrome/browser/firstrun/FirstRunSignInProcessor.java?rcl=11601c08e92732d2883af2057c41c17cba890844&l=87). Sadly, directly opening settings from there doesn't seem to work for some reason -- the Preferences activity and AccountManagementFragment are started, but then immediately paused again. There might be some timing issue that is usually avoided when signing in first.