Why is Telemachus initially doubtful that the man before him is his father?

Telemachus is initially doubtful that the man before him is his father, Odysseus, because he has not seen him in over twenty years and has only heard stories about him. Additionally, Odysseus appears in disguise, which adds to Telemachus's uncertainty. He struggles to reconcile the image of his father he has held onto with the stranger standing before him, leading to hesitance in accepting his true identity.