Automatic Indexing on Autonomous Database not working?

User_2IF27

In a free tier instance of an ATP database I have auto-indexing turned on in as evidenced by:

SELECT parameter_value 
FROM dba_auto_index_config
WHERE parameter_name = 'AUTO_INDEX_MODE'

PARAMETER_VALUE
------------------
IMPLEMENT

I've tried creating and populating tables with ~ 2 million rows, collected statistics, then queried them with very selective values, which should have made auto-indexing kick in. But checking dba_indexes for those tables shows no indexes and the auto-index reports show nothing.

Richard Foote wrote about this in December 2020, but had a subsequent post saying that the issue has been fixed (at least in the Sydney data center). I'm using the US East (Auburn) data center, and still seeing this problem though.

Anyone else experiencing this, or have any insight?