The contradiction is resolved if you go with either Ganguli's or Debroy's translation of verse 11.6. According to both, adṛṣṭa-pūrvāṇi (never seen before) means 'never seen before, by you [Arjuna].'
K. M. Ganguli's translation of Ch. 11, verses 4-8:
If, O Lord, thou thinkest that I am competent to behold that (form), then, O Lord of mystic power, show me thy eternal Self.
The Holy One said, 'Behold, O son of Pritha, my forms by hundreds and thousands, various, divine, diverse in hue and shape.
Behold the Adityas, the Vasus, the Rudras, the Aswins, and the Maruts. Behold, O Bharata, innumerable marvels unseen before (by thee).
Behold, O thou of curly hair, the entire universe of mobiles and immobiles, collected together in this body of mine, whatever else thou mayst wish to see.
Thou art, however, not competent to behold me with this eye of thine. I give thee celestial sight. Behold my sovereign mystic nature.'
Bibek Debroy translates it the same way:
Chapter 893 (33)
Arjuna said, 'Out of compassion for me, the extremely secret adhyatma
knowledge that you have stated has destroyed this delusion of mine. O
one with eyes like lotus leaves! From you I have heard in detail
about the creation and destruction of all beings, and also your
eternal greatness. O supreme lord! What you have said about yourself
is indeed like that. O supreme being! I wish to see your divine form.
O lord! If you think that I am worthy of seeing that, then, O lord of
yoga, show me your indestructible self.'
The lord said, 'O Partha! Behold my divine multi-dimensioned,
multi-hued, multi-shaped hundreds and thousands of forms. O
descendant of the Bharata lineage! See the adityas, the vasus, the
rudras, the ashvinis and the maruts. See the many wonderful things
you have never seen before. O Gudakesha! In my body, in one place,
see the entire universe, with all that is moveable and immovable.
Also see today, whatever else you want to see. You will not be able
to see me with your own eyes. Therefore, I am giving you divine sight.
Witness my divine glory.'
Sanjaya said, "O king! Having said this, Hari, the great lord of yoga, then
showed Partha the divine and supreme form—with many mouths and eyes, with
many miraculous things to see, adorned in many resplendent ornaments, with
many divine weapons raised, with divine garlands and clothing, anointed with
divine fragrances, extremely wonderful everywhere, resplendent, infinite, with
faces in every direction. If the brilliance of a thousand suns simultaneously rises
in the sky, then that brilliance can rival the brilliance of that great soul. Then
Pandava saw the entire universe in one place, divided into many parts, in that
great god of gods' body. Then, amazed and with his body hair standing up,
Dhananjaya bowed down before the god with his head lowered and, with joined
I don't see any difference between this form of Kṛṣṇa and the one he showed earlier in Dhṛtarāṣṭra's court as both of them required divine sight.
Chapter 792 (129)
Vaishampayana said, 'When Vidura spoke in this way, the valiant Keshava, the
destroyer of large numbers of the enemy, spoke to Duryodhana, Dhritarashtra's
son. "O Suyodhana! In your folly, you think of me as a single person. O one with
extremely evil intelligence! You desire to overpower and capture me. Here are
all the Pandavas, and the Andhakas and the Vrishnis. Here are the Adityas, the
Rudras, the Vasus and the maharshis."
Saying this, Keshava, the destroyer of
enemy warriors, laughed out aloud. When the great-souled Shouri was
laughing, the thirty gods sprouted from his sides. They were like lightning, but
were as small as a thumb. They were as radiant as the fire. Brahma appeared on
his forehead and Rudra on his chest. The guardians of the world were on his
arms and Agni was created from his mouth. The Adityas, the Sadhyas, the
Vasus, the Ashvins, Indra and the Maruts and the Vishvadevas manifested
themselves and the forms of the yakshas, the gandharvas and the rakshasas also
appeared. Sankarshana and Dhananjaya appeared on his two arms, the
archer Arjuna on the right and Rama, the wielder of the plough, on the left.
Bhima, Yudhishthira and Madri's two sons appeared on his back. The Andhakas
and the Vrishnis, with Pradyumna at the head, appeared in front of Krishna,
with their great weapons raised up. The conch shell, the chakra, the club, the
spear, the Sharnga, the plough and Nandaka could be seen. And many
other weapons were raised up. They were radiant in all the directions, around
Krishna's many arms. From his eyes, nose and ears emerged extremely terrible
flames of fire with smoke. Rays like those of the sun emerged from the pores of
his body. When they saw the terrible form of the great-souled Keshava, all the
kings were frightened in their hearts and closed their eyes, with the exception of
Drona, Bhishma, the immensely intelligent Vidura, the immensely fortunate
Sanjaya and the rishis, rich in austerities, because the illustrious Janardana
gave them divine sight.