I don't think the author of that understands what "public interest" means in the legal context. Fans of rival clubs and journalists being nosy doesn't constitute legal "public interest".
This is business between a private company and a sport's governing body. It's actually got fuck all to do with the public other than seeing an alleged criminal brought to justice by the proper, public, prosecuting authorities.
This is the same as the whistleblower argument.
It's my understanding that to be a whistleblwoer under UK law you have to be disclosing something illegal or the coverup of something illegal.
Breaking FFP or any UEFA rule is not a crime.