Juraj, thanks for your comment, but this limitation can be reliefed quite easily. There are a few points to consider:
- It is still possible to define only relevant searchable content by setting "Indexed content" for the index
- In this setting you can select only those page types, which are "pages" (have "Use Page Tab" enabled, for example) and specify root path ("/%" for all pages)
To be honest, I can't think of the cases where some entities of the same page type can be pages but some others cannot.