NodeType configurations don't get loaded

Using Neos & Flow Frontend & Integration
1

I’ve got several NodeTypes configured in my sitepackage. They all get loaded and work fine. But when I try to change a baseMixin or any other NEOS node this way:

'Neos.NodeTypes:Text':
  propertiesX:
    text:
       ...

In a file: “NodeTypes.Content.Text.yaml” in the same directory as the other configurations are: “Vendor.SitePackage/Configuration/”: The configuration is not loaded and there is no error. But there should be an error in NEOS backend in Configuration -> NodeTypes because I specified propertiesX just for test.

Now when I put the configuration inside of one of my other existing files: “NodeTypes.Content.Gallery.yaml”, which contains one of my own nodetype configurations:

'Vendor.SitePackage:Galery:':
  superTypes:
    'Neos.Neos:Content': true
    ...

'Neos.NodeTypes:Text':
  propertiesX:
    text:
      ...

Then the configuration is loaded and the error shows up.

Why this?

As far as I know from documentation, there is no setting that would exclude special files in sitepackage/Configuration.