I saw one comment in another forum which saying,
Was the dependent arising taught to an Arya ? No. It was first taught to the five ascetics, they were Non-arya then. Since an Arya has already seen the Dhamma, he only needs to deepen the insights.
What do you think?
And we also know in the suttas, the sotapanna state is described as a comprehension about
“yam kinci samudaya dhammam sabban tam nirodhadhammam”
Paṭiccasamuppāda is not just a book knowledge (though book knowledge is important).
I think those commenters are just wrong. One can understand Paṭiccasamuppāda correctly through books but yet the full extent of the Truth cannot be penetrated with developing meditation.
Even Ariya like Sotapanna, though gaining understanding in this teaching and have perfect confidence in this teaching, much works still need to be done. There will be degrees of understanding.
So, again and again, the Buddha teaches Paṭiccasamuppāda in many occasions. Such example will be Mahanidana sutta, though Ananda Thera understood it (he is a Sotapanna by that time), still the Buddha taught Mahanidana sutta to him.
Ariya Puggala are four types. The highest are arahants.
Arahants do not need to learn anymore. They have cut off all attachments. They have no more work to do in terms of “deepening the insights.” Their duty is to teach, to inform others and maintain Buddha Sasana (Buddha Dhamma). However, arahants do not know everything taught by the Buddha, although they know the Four Noble Truths by means of bhavanamaya nana. They still need to learn Buddha’s words and Pali language.
I guess the commenter mentioned in OP seems saying “since one realizes paticcasamuppada when he become sotapanna, he doesn’t need realizing it again apart from deepening the insight about three characteristics”.
Sotapanna cuts off Sakkaya Ditthi. A sotapanna has not realized the higher dhamma and does not have the knowledge of the arahants. A sotapanna is not very different from laypeople, except his knowledge of non-self, whish is the limit of sotapatti phala.