“However, if you read the rest of the sutta, the Buddha explains to bhikkhu Susima that pannavimutta Arahants get there by just seeing the anicca nature with wisdom”. (Lal)
I also belief this is being described but the sutta does not really teach that all those arahant were not abiding in any jhana. This is not mentioned. Arupavacara jhana is mentioned. It does not really teach that rupavacara jhana is not needed.
Also in MN70 this person, the one liberated by wisdom, is refered to as one who does not abide in arupavacara jhana but again does not mention the non-abiding of rupa vacara jhana.
Is attainment of rupavacara jhana not needed to become an arahant? Based on this sutta fragments i cannot conclude this for sure. I will re-read the post.
Siebe