A demonstrative can point to a physically visible referent; it can also evoke a person or event present to the audience's mind. Classical rhetorical examples therefore employ demonstratives for people who are not standing before the speaker.
Physical pointing: «هٰذَا صَدِيقِي» — “This is my friend,” when the person is present.
Mental reference: after recalling celebrated scholars, «أُولٰئِكَ أَئِمَّتُنَا» — “Those are our leaders.”
Restricting all demonstratives to physical distance misses their role in praise, disparagement, and magnification. Context must establish which referent the speaker intends and how the audience identifies it.