Secure Upload File URLs Changing to uploads/short-url in Public Categories

Secure Upload is enabled, and the S3 file links changes when editing a Topic with files:

from secure-uploads/original/... → to uploads/short-url/...

This only happens in Public Categories.

Is this expected behavior, a bug, or am I missing a setting?

Yes, it is supposed to be like that.

thank you but why this is not the case with Private Categories?