Disclaimer on state modified behavior change (#6357)

## What are you changing in this pull request and why?

Closes #6247

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<!-- vercel-deployment-preview -->
---
🚀 Deployment available! Here are the direct links to the updated files:


-
https://docs-getdbt-com-git-state-comparison-dbt-labs.vercel.app/reference/global-configs/behavior-changes
-
https://docs-getdbt-com-git-state-comparison-dbt-labs.vercel.app/reference/node-selection/state-comparison-caveats

<!-- end-vercel-deployment-preview -->

---------

Co-authored-by: Mirna Wong <[email protected]>
Co-authored-by: Leona B. Campbell <[email protected]>
Co-authored-by: runleonarun <[email protected]>

website/docs/reference/global-configs/behavior-changes.md

@@ -4,6 +4,8 @@ id: "behavior-changes"
 sidebar: "Behavior changes"
 ---
 
+import StateModified from '/snippets/_state-modified-compare.md';
+
 Most flags exist to configure runtime behaviors with multiple valid choices. The right choice may vary based on the environment, user preference, or the specific invocation.
 
 Another category of flags provides existing projects with a migration window for runtime behaviors that are changing in newer releases of dbt. These flags help us achieve a balance between these goals, which can otherwise be in tension, by:
@@ -83,13 +85,18 @@ Set the `skip_nodes_if_on_run_start_fails` flag to `True` to skip all selected r
 
 ### Source definitions for state:modified
 
+:::info
+
+<StateModified features={'/snippets/_state-modified-compare.md'}/>
+
+:::
+
 The flag is `False` by default.
 
 Set `state_modified_compare_more_unrendered_values` to `True` to reduce false positives during `state:modified` checks (especially when configs differ by target environment like `prod` vs. `dev`).
 
 Setting the flag to `True` changes the `state:modified` comparison from using rendered values to unrendered values instead. It accomplishes this by persisting `unrendered_config` during model parsing and `unrendered_database` and `unrendered_schema` configs during source parsing.
 
-
 ###  Package override for built-in materialization 
 
 Setting the `require_explicit_package_overrides_for_builtin_materializations` flag to `True` prevents this automatic override. 

website/docs/reference/node-selection/state-comparison-caveats.md

@@ -2,6 +2,8 @@
 title: "Caveats to state comparison"
 ---
 
+import StateModified from '/snippets/_state-modified-compare.md';
+
 The [`state:` selection method](/reference/node-selection/methods#the-state-method) is a powerful feature, with a lot of underlying complexity. Below are a handful of considerations when setting up automated jobs that leverage state comparison.
 
 ### Seeds
@@ -48,6 +50,8 @@ dbt test -s "state:modified" --exclude "test_name:relationships"
 
 To reduce false positives during `state:modified` selection due to env-aware logic, you can set the `state_modified_compare_more_unrendered_values` [behavior flag](/reference/global-configs/behavior-changes#behavior-change-flags) to `True`.
 
+<StateModified features={'/snippets/_state-modified-compare.md'}/>
+
 </VersionBlock>
 
 <VersionBlock lastVersion="1.8">

website/snippets/_state-modified-compare.md

@@ -0,0 +1,3 @@
+You need to build the state directory using dbt v1.9 or higher, or [Versionless](/docs/dbt-versions/versionless-cloud) dbt Cloud, and you need to set `state_modified_compare_more_unrendered_values` to `true` within your dbt_project.yml.
+
+If the state directory was built with an older dbt version or if the `state_modified_compare_more_unrendered_values` behavior change flag was either not set or set to `false`, you need to rebuild the state directory to avoid false positives during state comparison with `state:modified`.