Proof of credentials - for authors of recommendation letters

The guideline states that each recommendation letter must 'Come with the author’s CV (or other proof of their credentials that the endorsing body will accept)

Will LinkedIn profile be sufficient?

Yes, a link to the individual’s LinkedIn profile can be provided.

All my recommenders had half a page, or about 2 paragraphs explain who they are, and a link to their LinkedIn profile either in header or under their signature.