Trace Flag 3688 not working on SQL Server 2014

We are using some third party tools that fill up the SQL Server logs with entries like:

SQL Trace ID 1 was started by login "sa".
SQL Trace ID 2 was started by login "XX\xxxxx".
SQL Trace stopped. Trace ID = '2'. Login Name = 'XX\xxxxx'.
SQL Trace ID 2 was started by login "XX\xxxxx".

I am trying to suppress these by enabling TF 3688 but it is not working on SQL Server 2014, 2012 or SQL 2008 R2. Here is a snapshot of the configuration. Please let me know if I am missing anything:

I have restarted the instance and verified that the trace flag is active using DBCC TRACESTATUS:

That trace flag isn't documented and shouldn't be used in production environments.

That said, it appears that the trace flag stopped working in SQL Server 2008 R2 and newer. As it's undocumented Microsoft won't take a support ticket to fix it as you shouldn't have been using an undocumented trace flag.

All undocumented commands and features can be changed at Microsoft's whim.

StackExchange Database Administrators Q#87216, answer score: 3