First, welcome to the Pantheon Community discussion board! Our docs are better because of the contributions of many, including those in our community. Thank you for taking the time to offer suggestions. 
Last updated: +1 great suggestion. “Freshness dates” give readers important cues that help build trust in the content.
Last year, we began adding visible “Last Reviewed” dates to docs, but not all have them yet (including this particular one). We are working to meet our goal of adding them to all our content, and I appreciate your support for that goal!
Why does this doc exist?: Our docs exist to help you be successful using Pantheon’s products and services.
Context: I really appreciate your note here on the importance of context in docs.
Pantheon’s platform is indeed opinionated, and our docs reflect that with best practices, based on the expertise of both our internal subject matter experts and also community contributors who build often-used and recommended tools.
If something is unsupported or experimental, the docs will note that.
It sounds like for this doc, it would be helpful to include additional context about how this tool fits into our best practices recommendations for API key management. Context is key; with that in mind, we will review this one to ensure these instructions fit into the larger context of ways to manage API keys with Pantheon sites.
I don’t know if you have Github credentials, but based on your feedback we’ve created an issue (DOCS 6235) you can track for this particular doc. If you’re available, I’d love to include you as a reviewer for the update to ensure we’re hitting the mark. Thanks again!