If I understand correctly Higgsfield has never had an issue with face references.
Example attached are the reference files used for a video.
What is NOT allowed are faces of famous people or intellectual property such as famous anime.
When adding an image or video it does a content check to make sure it's not protected content. For example Sailor Moon (Bishōjo Senshi Sērā Mūn) content is prohibited as that is a protected property.
I was also able to use reference files for Getartcraft and had no problems, as mentioned you should use their variation "Seedance 2.0 Plus Ultra" if your content has any content containing violence, gore, or nudity.