I am using the mechanism to override an .ftl, specifically to add .js "after" an existing js block e.g.
<@region id="additional-js" target="js" action="after" scope="global" />
This is for a Cloud override of a "js" region for search.get.html.ftl
If you create an override of that component for the js block e.g.:
When you view-source on the resulting page, I found that the new cloud-search.js was actually inserted between the two js files that happened to be in the original block! This obviously breaks the client-side component method override as the base component is not present at init time. Anyway, also I found that using the "before" or "after" did not seem to work (both did an insert in the middle) but "replace" does work which I have used as a work-around for now.
See the two search.get.html.ftl files in HEAD-BUG-FIX for concrete example)