With the solution https://issues.liferay.com/browse/LPS-119920 we have made a behavior change in Staging, for the way we use site page variations and their layouts. If a site page variation is deleted from the system, all the layouts that were added to the specific variation are also removed. If the user is on a layout that is going to be removed, a warning message will appear.
Please add the above part to our official documentation. The below article might be a good knowledge base:
If you have any questions please let me know.