Wrong join date and post count in reviewable insights

Steps to reproduce:

  1. Enable Reviewable UI refresh at least for the admin group.
  2. Use an admin user that was created a while ago and has a few posts.
  3. Flag one of your posts.
  4. Check the insights tab on the reviewable.

Expected result:
Trust level, join date, and number of posts are correct.

Actual result:
Trust level is correct, join date is today’s date, and the post count is 0.

The request seems to be for the right user (ID 29) and the data that is shown as the response seems correct too.