Update readme with notes about URL Metric collection

Fixes #1925

Author: westonruter

plugins/optimization-detective/readme.txt

@@ -13,9 +13,9 @@ Provides a framework for leveraging real user metrics to detect optimizations fo
 
 This plugin captures real user metrics about what elements are displayed on the page across a variety of device form factors (e.g. desktop, tablet, and phone) in order to apply loading optimizations which are not possible with WordPress’s current server-side heuristics.
 
-This plugin is a dependency which does not provide end-user functionality on its own. For that, please install the dependent plugin [Image Prioritizer](https://wordpress.org/plugins/image-prioritizer/) or [Embed Optimizer](https://wordpress.org/plugins/embed-optimizer/) (among [others](https://github.com/WordPress/performance/labels/%5BPlugin%5D%20Optimization%20Detective) to come from the WordPress Core Performance team). There are currently **no settings** and no user interface for this plugin since it is designed to work without any configuration.
+This plugin is a framework dependency which does not provide optimization functionality on its own. For that, please install the [Image Prioritizer](https://wordpress.org/plugins/image-prioritizer/) and [Embed Optimizer](https://wordpress.org/plugins/embed-optimizer/) dependent plugins (among [others](https://github.com/WordPress/performance/labels/%5BPlugin%5D%20Optimization%20Detective) to come from the WordPress Core Performance team). There are currently **no settings** and no user interface for this plugin since it is designed to work without any configuration.
 
-Your site must have the **REST API accessible** to frontend visitors since this is how metrics are collected about how a page should be optimized.
+Your site must currently have the **REST API accessible** to unauthenticated frontend visitors since this is how real user metrics are collected about pages on your site; nevertheless, [exploration](https://github.com/WordPress/performance/issues/1311) is underway for providing alternative mechanisms for collecting the metrics. Also, please note that no metrics are currently collected from Safari since it does not yet support the [Largest Contentful Paint](https://developer.mozilla.org/en-US/docs/Web/API/LargestContentfulPaint) metric, but support for this [Core Web Vitals](https://web.dev/explore/learn-core-web-vitals) metric is coming this year [via Interop 2025](https://webkit.org/blog/16458/announcing-interop-2025/#core-web-vitals).
 
 Please refer to the [full plugin documentation](https://github.com/WordPress/performance/blob/trunk/plugins/optimization-detective/docs/README.md) for a [technical introduction](https://github.com/WordPress/performance/blob/trunk/plugins/optimization-detective/docs/introduction.md), [filter/action hooks](https://github.com/WordPress/performance/blob/trunk/plugins/optimization-detective/docs/hooks.md), and [extensions](https://github.com/WordPress/performance/blob/trunk/plugins/optimization-detective/docs/extensions.md) that show use cases and examples.