In the "Site Creation" part of the settings, when selecting "A classic site" we're facing a "site classification" option.
Site classification concept is different when comparing sites with groups (tags) and classic sites (policy).
It was difficult to understand that when choosing the classic site option the classification field was linked with policies. And thus if the policy is not created at the site collection level this option is not showed to the end-user.

Suggestion: change the name of the field or put a text to explain it. Thus: tell administrator that this option is not activated unless he/she creates policies before.

Cheers,

Leonardo