Currently, the out of the box Primary association label for Contact and Company label can't be edited and is labelled as Primary.
Now when we use Primary association label when associating a contact to a company on viewing the contact record the right side view of the associated Company comes up with the label Primary which seems to be correct. But when we view the company record the right side view of the associated contact comes up with the label Primary Company (screenshot attached for reference). I believe the labels should either be reversed or it should just read as Primary for both.
Will highly recommend HubSpot look into fixing the naming convention on the contact-company Primary association label.