When my S5 contacts connected via links, why aren't the apps showing?

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AC Question

s5 contacts connected via links - apps not showing

When i select a contact from my phone contacts list, under the video call, messaging and call options there is a list with a "connected via" header showing the applications with which i am "linked" with that contact. I noticed that one contact is not showing linked via whatsapp in my phone contacts, and i can't start a chat with this contact from my phonebook by clicking the whatsapp logo but have to open the whatsapp messenger instead. What does this mean? Is it that this person doesn't actually have me saved as a contact on their phone and thats why we're not "linked"?