There's something really fascinating about how Athena treats Diomedes so differently from how treats Penelope and Odysseus (even Telemachus but that's a lil different too)

Athena has basically known Diomedes since he was born (some even say that she had a say in naming him) because of Tydeus. I don't think it's far-fetched to say that in a way, she possibly "molded" him. And Diomedes is kind of known for being the "perfect warrior king". He's respectful of the gods and most of his comrades, an incredibly skilled soldier, and has already achieved so many things despite being one of the youngest kings in the war.

I sadly think that's why Athena treats him so differently than Odysseus, Penelope, and Telemachus.

She cares for him, but it's still "distant" in a way. Or almost in an "I molded you. You will react the way I would want you to therefore I will not be surprised."

When it seems like she's known her other favored mortals for less long, she didn't get to "mold" them. They surprise and bring something "new" for her. She sees her little tricksters' scheme and plot and watches with intrigue but watching the perfect warrior is a "Yes, perfect form. That's what I'd do."

I mean even how her favored mortals pray to her tells you a lot about the relationships they have.

For example, in the Iliad, Odysseus doesn't need to really give as much reverence to her to "earn her favor" during book 10's Night Raid.

Odysseus rejoiced, and prayed to Pallas Athene: ‘Hear me, daughter of aegis-bearing Zeus, you who are with me in all my adventures, protecting me wherever I go. Show me your love, Athene, now, more than ever, and grant we return to the ships having won renown, with some brave act that will grieve the Trojans greatly.’ And Diomedes of the loud war-cry followed him in prayer: ‘Hear me also, Atrytone, daughter of Zeus. Be with me as you were with my father Tydeus in Thebes, when he went there as ambassador for the bronze-greaved Achaeans, camped there by the Asopus. A friendly offer was what he made them, but on his way back he was forced to take deadly reprisal for their ambush, and you fair goddess, readily stood by him. Stand by me now, and watch over me, and in return I will offer a broad-browed yearling heifer, unused to the yoke. I will tip her horns with gold and sacrifice her to you.’

(Book 10, A.S. Kline)

Diomedes brings up his dad and offers a young heifer (granted that could just be how Diomedes is with every immortal) while Odysseus doesn't and is basically like "Yo, help me out like you always do!". Odysseus is much more casual and personal with Athena. And with Penelope, Athena takes the form of one of her sisters to comfort her!

While Athena also most likely has known Telemachus since he was a baby, she's still closer to him than Diomedes.

Imagine that. You're basically molded by a goddess since birth, listen to her and other immortals dutifully, basically become her perfect warrior, and yet you can't seem to reach that familiarity with her. The same warmth she has for her other favored mortals.