In a recent facebook discussion, it seemed that everyone had difficulty with knowing how people looked when the person is not present. Even very familiar people can be difficult to describe as we can not see a picture of the person in our minds. We rely on describing the "facts" (verbal descriptions) we know about the person.
But once the person is present we vary. Many of us have no problem / are very good at recognizing faces when we see someone. Some other people with aphantasia also have difficulty recognizing faces especially when they see someone out of context. Others tend not to notice people out of context and only recognize them after they are called to their attention.