missing threshold logging tracer output with simple test

Scenario:
Simple test that sets the timeout threshold low, then does a bunch of ops in a tight loop. Then does more ops for 20 seconds.

Expected behavior:
ThresholdLoggingTracer would log something

Observed behavior:
Some minorly enhanced timeout logging, but no threshold logging tracer output.

Script and output attached. Invoked as:
$ LCB_LOGLEVEL=2 python timeoutme.py > run.out 2>&1

(note: filing this to Sergey Avseyev since it probably is lcb level, but I wrote the test as python, please move or redirect as appropriate)