The -T option for format.sh is generating calls to the t binary with the trace arguments in the wrong spot, and a spurious double-comma where they should be for example, running ./format.sh -a -t 10 -T bulk,txn,retain=100 runs t like ./t -c /home/ubuntu/dev/wt-9584/wiredtiger/build/test/format/CONFIG.stress -h /home/ubuntu/dev/wt-9584/wiredtiger/build/test/format/RUNDIR.8 -T ,, format.abort=1 bulk,txn,retain=100 quiet=1.

It's not clear to me whether this is just an issue with how it's being printed, or if t is actually running with incorrect tracing arguments.