Linking personas creates new persona
When linking a personas folks creates a new persona https://gitlab.gnome.org/GNOME/folks/blob/master/folks/individual-aggregator.vala#L2178. The new persona shows in Evolution as a contact with no properties. Also the persona isn't removed when the individual is unlinked. It looks like this persona isn't even needed because I can remove it from the store after linking about without any issue.
I would expect that linking doesn't modify the storage and doesn't create empty contacts.