Here is a part of this sutta. I will highlight relevant parts for discussion:
There the Venerable Mahāmoggallāna addressed the bhikkhus: “Friends, bhikkhus!”
“Friend,” those bhikkhus replied. The Venerable Mahāmoggallāna said this:
“Here, friends, a bhikkhu declares final knowledge thus: ‘I understand: “Destroyed is birth, the spiritual life has been lived, what had to be done has been done, there is no more coming back to any state of being.”’ The Tathāgata [156] or his disciple who is a jhāna-attainer—skilled in attainment, skilled in others’ minds, skilled in the ways of others’ minds—questions him, interrogates him, and cross-examines him. When he is being questioned, interrogated, and cross-examined by the Tathāgata or his disciple, he comes to an impasse and is flustered. He meets with calamity, meets with disaster, meets with calamity and disaster.
“The Tathāgata or his disciple who is a jhāna-attainer . . . encompasses his mind with his own mind and considers: ‘Why does this venerable one declare final knowledge thus: “I understand: ‘Destroyed is birth, the spiritual life has been lived, what had to be done has been done, there is no more coming back to any state of being.’”?’ The Tathāgata or his disciple, having encompassed his mind with his own mind, understands:
(1) “‘This venerable one is prone to anger and his mind is often obsessed by anger. But in the Dhamma and discipline proclaimed by the Tathāgata, obsession by anger is a case of decline.
(2) “‘This venerable one is hostile and his mind is often obsessed by hostility. But in the Dhamma and discipline proclaimed by the Tathāgata, obsession by hostility is a case of decline.
So, this is a case of a monk claiming he is enlightened, but it was a false claim, right?
Now, in the Sumsīma Sutta, we also have monks claiming they are enlightened. And I do not see anywhere in the sutta that the Buddha actually says they are indeed enlightened, despite the fact that tradition has accepted that they are.
If there anything to suggest that these monks are definitely also not making a false claim there, as they are here in this sutta? And is this not supported by the fact that Susīma is also asked at the end of the sutta:
“But knowing and seeing thus, do you wield the many kinds of psychic power?
He knew and saw things, but did not have those psychic powers. And he was not an arahant. And this was the Buddha’s answer to Susīma regarding how it could be that those guys could claim they were arahants but not have those powers. And he basically leaves it at that!
So should Susīma not take this to mean that since he knows and sees, but doesn’t have powers, and is not an arahant himself, this explains that those others also might know and see, but are not arahants, which is why neither Susīma nor they have those powers.
See here how the conversation ends:
“Well now, Susīma, how could there be such a declaration when these things are not attained?”
“Ettha dāni, susima, idañca veyyākaraṇaṃ imesañca dhammānaṃ asamāpatti, idaṃ no, susima, kathan”ti?
Then Venerable Susīma bowed with his head at the Buddha’s feet and said:
Atha kho āyasmā susimo bhagavato pādesu sirasā nipatitvā bhagavantaṃ etadavoca:
So that’s the end of that discussion. No actual direct answer on whether they were enlightened or not, but the implicit answer that they were not, it could seem.
Then rather randomly we seem to have skipped to another topic, Susīma apologising for his motivation (maybe because he now respected the Buddha for his wisdom in replying to his query):
“I have made a mistake, sir. It was foolish, stupid, and unskillful of me to go forth as a thief in such a well-explained teaching and training.
“accayo maṃ, bhante, accagamā yathābālaṃ yathāmūḷhaṃ yathāakusalaṃ, yvāhaṃ evaṃ svākkhāte dhammavinaye dhammatthenako pabbajito.