Add a note about the difference between hostname and zone level AOP

[sorodeji]

Summary

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Documentation checklist

• Is there a changelog entry (guidelines)? If you don't add one for something awesome and new (however small) — how will our customers find out? Changelogs are automatically posted to RSS feeds, the Discord, and X.
• The change adheres to the documentation style guide.
• If a larger change - such as adding a new page- an issue has been opened in relation to any incorrect or out of date information that this PR fixes.
• Files which have changed name or location have been allocated redirects.

[RebeccaTamachiro]

Thanks for the PR!
I've also created PCX-19912 for myself to further improve AOP docs.