The configuration item transaction.timestamps indicates whether timestamps should be in use or not during a test/format run. While disabled, after a test/format run, we can see the following in the metadata file:

../../wt -r -h RUNDIR/ dump file:WiredTiger.wt

...
system:oldest\00
oldest_timestamp="4",checkpoint_time=1712269181,write_gen=7\00
...

We should not be setting the oldest ts. This is because timestamp_teardown is called at the end of a run without checking if timestamps are in use.