docs: correct default for router extra option (#32702)

PR Close #32702

packages/router/src/router_module.ts

@@ -233,16 +233,17 @@ export function provideRoutes(routes: Routes): any {
  * Allowed values in an `ExtraOptions` object that configure
  * when the router performs the initial navigation operation.
  *
- * * 'enabled' (Default) The initial navigation starts before the root component is created.
- * The bootstrap is blocked until the initial navigation is complete.
+ * * 'enabled' - The initial navigation starts before the root component is created.
+ * The bootstrap is blocked until the initial navigation is complete. This value is required
+ * for [server-side rendering](guide/universal) to work.
  * * 'disabled' - The initial navigation is not performed. The location listener is set up before
  * the root component gets created. Use if there is a reason to have
  * more control over when the router starts its initial navigation due to some complex
  * initialization logic.
- * * 'legacy_enabled'- The initial navigation starts after the root component has been created.
+ * * 'legacy_enabled'- (Default, for compatibility.) The initial navigation starts after the root component has been created.
  * The bootstrap is not blocked until the initial navigation is complete. @deprecated
  * * 'legacy_disabled'- The initial navigation is not performed. The location listener is set up
- * after the root component gets created. @deprecated
+ * after the root component gets created. @deprecated since v4
  * * `true` - same as 'legacy_enabled'. @deprecated since v4
  * * `false` - same as 'legacy_disabled'. @deprecated since v4
  *
@@ -275,11 +276,24 @@ export interface ExtraOptions {
   useHash?: boolean;
 
   /**
-   * One of `enabled` (the default) or `disabled`.
-   * By default, the initial navigation starts before the root component is created.
-   * The bootstrap is blocked until the initial navigation is complete.
+   * One of `enabled` or `disabled`.
+   * When set to `enabled`, the initial navigation starts before the root component is created.
+   * The bootstrap is blocked until the initial navigation is complete. This value is required for
+   * [server-side rendering](guide/universal) to work.
    * When set to `disabled`, the initial navigation is not performed.
    * The location listener is set up before the root component gets created.
+   * Use if there is a reason to have more control over when the router
+   * starts its initial navigation due to some complex initialization logic.
+   *
+   * Legacy values are deprecated since v4 and should not be used for new applications:
+   *
+   * * `legacy_enabled` - Default for compatibility.
+   * The initial navigation starts after the root component has been created,
+   * but the bootstrap is not blocked until the initial navigation is complete.
+   * * `legacy_disabled` - The initial navigation is not performed.
+   * The location listener is set up after the root component gets created.
+   * * `true` - same as `legacy_enabled`.
+   * * `false` - same as `legacy_disabled`.
    */
   initialNavigation?: InitialNavigation;