“Therefore, unlike the other five abhiññās, asavakkhaya nana seems to be achievable without jhana.”
– Yes. As I have mentioned in various posts/comments, cultivating jhanas is not necessary to attain any stage of Nibbana, even though they may be realized at various stages of Nibbana.
– That is clear, for example, from the two types of citta vithi involved in getting to jhana and magga phala at the end of the following post:
“Citta Vīthi – Processing of Sense Inputs”
– What are the “other five abhiññās” you mentioned?