There are two two aspects to this issue:
- I have seen Samma Samadhi described this way in a few other suttas too.
- On the other hand, there are many accounts in the Tipitaka where people attained various stages of magga phala just by listening to a single desana by the Buddha.
So, here is my explanation.
After “completing” Samma Samadhi, one goes through two more stages to attain the Arahanthood: Samma Nana and Samma Vimutti.
It is said that “atthangehi samannagato Sekha, dasa angehi samannagato Arahant” or “one completing the eightfold Path is a Trainee (Sekha), one who has completed the 10 steps is an Arahant“.
The description in terms of jhanas holds when Samma Samadhi is “complete” or almost complete and when one has attained the fourth Ariya jhana. As discussed in the subsection referenced below, one is at least an Anagami when attaining the fourth Ariya jhana.
There are two ways one can become an Arahant: Pannavimutta or cetovimutta.
– A pannavimutta Arahant may attain the Arahanthood without going through jhana (like those who attained Arahant phala while listening to their very first desana). However, once the Arahantohood is attained, all four rupavacara jhana are automatically attained. In some cases (like minister Santati and Culapanthaka Thero), even iddhi (supernormal) powers are attained with the Arahanthood. In the case of Santati (who was wearing royal robes and was riding an elephant), he attained Arahanthood just listening to a single verse by the Buddha. He was about to die and the Buddha asked him to show evidence to others that he had attained Arahanthood. Santati obliged by leaping up and burning himself with tejo kasina at the moment of death.
– A cetovimutti Arahant goes through the jhanic states and attains Arahanthood after completing both rupavacara and arupavacara jhana.
Therefore, either way, one completes Samma Samadhi (attaining the four rupavacara jhanas), before attaining the Arahanthood.
These are discussed in the section: “Samādhi, Jhāna (Dhyāna), Magga Phala“.