Only output verbose details for parentwork plugin when running explicitly

[aereaux]

Description

Fixes #4120.

This may not be the fully desired behavior, let me know if there's anything I should tweak.,

To Do

• Documentation. (If you've added a new command-line flag, for example, find the appropriate page under docs/ to describe it.)
• Changelog. (Add an entry to docs/changelog.rst to the bottom of one of the lists near the top of the document.)
• Tests. (Very much encouraged but not strictly required.)