B.G 4.04
अर्जुन उवाच
अपरं भवतो जन्म परं जन्म विवस्वतः। कथमेतद् विजानीयां त्वमादौ प्रोक्तवानिति ॥४॥
arjuna uvāca
aparaṁ bhavatō janma paraṁ janma vivasvataḥ। kathamētad vijānīyāṁ tvamādau prōktavāniti ॥4॥
[अर्जुन उवाच अपरं भवतो जन्म परं जन्म विवस्वतः। कथम् एतद् विजानीयां त्वम् आदौ प्रोक्तवान् इति॥
arjuna uvāca = Arjuna asked; aparaṁ = recent; bhavatō = yours; janma = birth; paraṁ = earlier/remote; janma = is the birth; vivasvataḥ = of Vivasvata;। katham = How; ētad = this; vijānīyāṁ = to understand; tvam = by you; ādau = in the beginning; prōktavān = taught; iti = thus;॥]
Arjuna asked:
Recent in time is your birth, and remote in antiquity was the birth of Vivasvan. How then am I to understand that you taught it in the beginning?
Gīta Tātparya 4.04
Those who are wise ask questions to bring unique wisdom to the forefront of society.
जानन्तोऽपि विशेषार्थज्ञानाय स्थापनाय वा। पृच्छन्ति साधवो यस्मात् तेन पृच्छसि पार्थिव॥
jānantō'pi viśēṣārthajñānāya sthāpanāya vā। pr̥cchanti sādhavō yasmāt tēna pr̥cchasi pārthiva॥
[jānantō'pi = even after knowing; viśēṣārthajñānāya = to know special knowledge; sthāpanāya = for the establishment; vā = as well;। pr̥cchanti = asks; sādhavō = the wise; yasmāt = because; tēna = by that; pr̥cchasi = you ask; pārthiva = O son of Pritha;॥]
"Even though they have previous understanding, the wise ask question about the special knowledge to establish, and to ascertain. Similarly, Arjuna inquired."
इति आग्नेयवचनात् न अर्जुनः भगवन्तं न जानाति ॥४॥
iti āgnēyavacanāt na arjunaḥ bhagavantaṁ na jānāti ॥4॥
[ iti = thus; āgnēyavacanāt = statement of Agni Purāna; na = not; arjunaḥ = Arjuna; bhagavantaṁ = the lord; na = not; jānāti = knows;॥]
From such statements of Agni Purāna, it becomes clear Arjuna is not asking because he doesn't know the Lord.