A pardon does not automatically require a confession (though it could be part of the terms), however blanket pardons remove the ability to plead the 5th on the topic if subpoenaed as a witness. The 5th precludes being forced to testify against yourself, but if the government has declared it not a crime then you can’t testify against yourself even if you wanted to.

From what I recall, non-global pardons still maintained some level of 5th Amendment protections. Ie you were pardoned for A, but talking about A might reveal you did B, so you could still potentially testify against yourself.

Iirc, non-global pardons usually come with a stipulation like “must testify that or about…” because of this.

And was a campaign promise Trump issued in order to secure votes from that base.