Odoo website builder will replace a view if it contains something like this and the user edits that section:

<div class="oe_structure"/>

However, since Odoo v12, if it is in this other format, instead of creating a COW view that completely replaces the previous one, it will create an extension view that replaces this specific element in the parent view:

<div id="oe_structure_SOME_HOOK_HERE" class="oe_structure"/>

This provides a more resilient upgrade path because your module can "safely"* update the base view which contains logic, while user customizations are kept separately.

IMHO this is a good candidate for a linter.

* You know that in Odoo nothing is exactly "safe", but it's better. 🤷