One workflow, five versions. Four of the five are started by 02_MONITOR through Workflow Service Input, and nothing in here knows that. Send nothing and the declared workflow variables are used instead, which is why it still runs on its own.
It makes its own registry. Both writers sit on the LOCAL file system and work their absolute path out at run time, so the folder, the model file and registry.csv all appear on a first press with no registry/ beside them.
Why two fits, why rows_trained is not rows_measured, why the solver tolerance is 1e-8 and why created_at is the one column verify.py skips: README.md.