Content Previewer typesetting vs mobi

Hello!

When you would like to see how a document looks like on a Kindle ereader, you can use Kindle Previewer program and it can determine whether the document is suitable for enhanced typesetting or not.

As far as I know it is about hyphenation, kerning, ligatures etc..

AFAIK These characteristics are only available for azw3 and kfx.

So let's say the program says your document is suitable for enhanced typesetting, but then it offers only to save the document to .mobi or .azk. WHY?!