Clarify documentation for relaxed binding of environment variables

Closes gh-22974

Author: wilkinsona

spring-boot-project/spring-boot-docs/src/main/asciidoc/spring-boot-features.adoc

@@ -1185,9 +1185,6 @@ To convert a property name in the canonical-form to an environment variable name
 
 For example, the configuration property `spring.main.log-startup-info` would be an environment variable named `SPRING_MAIN_LOGSTARTUPINFO`.
 
-NOTE: Underscores cannot be used to replace the dashes in property names.
-If you attempt to use `SPRING_MAIN_LOG_STARTUP_INFO` with the example above, no value will be bound.
-
 Environment variables can also be used when binding to object lists.
 To bind to a `List`, the element number should be surrounded with underscores in the variable name.
 
@@ -1461,7 +1458,7 @@ The following table summarizes the features that are supported by `@Configuratio
 
 | <<boot-features-external-config-relaxed-binding,Relaxed binding>>
 | Yes
-| Limited (see note below)
+| Limited (see <<boot-features-external-config-vs-value-note,note below>>)
 
 | <<appendix-configuration-metadata.adoc#configuration-metadata,Meta-data support>>
 | Yes
@@ -1472,15 +1469,15 @@ The following table summarizes the features that are supported by `@Configuratio
 | Yes
 |===
 
-If you define a set of configuration keys for your own components, we recommend you group them in a POJO annotated with `@ConfigurationProperties`.
-Doing so will provide you with structured, type-safe object that you can inject into your own beans.
-
-If you do want to use `@Value`, we recommend that you refer to property names using their canonical form (kebab-case using only lowercase letters).
+NOTE: [[boot-features-external-config-vs-value-note]] If you do want to use `@Value`, we recommend that you refer to property names using their canonical form (kebab-case using only lowercase letters).
 This will allow Spring Boot to use the same logic as it does when relaxed binding `@ConfigurationProperties`.
 For example, `@Value("{demo.item-price}")` will pick up `demo.item-price` and `demo.itemPrice` forms from the `application.properties` file, as well as `DEMO_ITEMPRICE` from the system environment.
 If you used `@Value("{demo.itemPrice}")` instead, `demo.item-price` and `DEMO_ITEMPRICE` would not be considered.
 
-Finally, while you can write a `SpEL` expression in `@Value`, such expressions are not processed from <<boot-features-external-config-application-property-files,application property files>>.
+If you define a set of configuration keys for your own components, we recommend you group them in a POJO annotated with `@ConfigurationProperties`.
+Doing so will provide you with structured, type-safe object that you can inject into your own beans.
+
+While you can write a `SpEL` expression in `@Value`, such expressions are not processed from <<boot-features-external-config-application-property-files,application property files>>.