If a contact is deleted the following will be deleted
- All standar data except first name and last name (Phone, Email, titel etc.)
- Custom field data
The reason some data is saved is to get version handling on account level. In Salesbox its possible to see the contact name on old/historic tasks, leads, opportunities but open the contact card. All activity and sales stats are also kept to not affect and stats.
This support the new EU regulations for data integrity for private people (GDPR) since no personal information is kept.