This is only here to document the legacy of how we got to this situation.
Long ago validation created its own system to parse environmental variables as well as the vk_layer_settings.txt flow.
Then we created VK_EXT_validation_features as way to set things at vkCreateInstance time. VK_EXT_validation_flags was also created after with the same goals in mind.
As more and more layers basically needed to do what Validation Layers were doing, we just ended up creating VK_EXT_layer_settings as a final solution. This extension has been the way forward to a better system of creating settings for layers.
Unfortunately, we still support some legacy names, so this prevents us from making everything consistent.