@danbri @28development Any news on this?

Echoing @danbri's comment:
This looks like a Google issue not a Schema.org thing.
the Schema.org definition doesn’t talk about “Confidential” as a special value for https://schema.org/hiringOrganization

Looking at Googles writings on this there is some confusion and lack of clarity.

Firstly they say this in documentation:
If the organization is hiring anonymously (for example, a staffing agency on behalf of an anonymous employer or an employer directly on your platform), use the confidential value for the HiringOrganization field.
However, there is no clarification as to what the confidential value is - or is it just the string "confidential"?

Elsewhere there is this in a Google support conversation:
I don't know which documents you are referring to, but this markup complies with Google's ban:

Jobs or content that represent the employer in a way that is not accurate, realistic, or truthful.

Also this markup contradicts Google:

hiringOrganization Organization
The organization offering the job position. This must be the name of the company

As a data consumer, some clarity from Google would be helpful.

One option for Schema.org could be to to define a specific value in the vocabulary to represent this state of a confidential organization. However, this would then raise issues of where this would be applicable and which data consumers may adopt it.