DN 15 & also AN 7.44 exclusively include the utterance of the "seven stations of consciousness", where the later six equate with the six of the eight jhanas, namely:
1. There are sentient beings that are diverse in body (kāyā) and diverse in perception (saññino), such as human beings, some gods (devā) and some beings in the underworld.
2. There are sentient beings that are diverse in body and unified in perception, such as the gods reborn (ābhinibbattā) in Brahmā’s Group (brahmakāyikā) through the first absorption
3. There are sentient beings that are unified in body and diverse in perception, such as the gods of streaming radiance (ābhassarā).
4. There are sentient beings that are unified in body and unified in perception, such as the gods replete with glory (subhakiṇhā).
5. There are sentient beings that have gone totally beyond perceptions of form (rūpa). With the ending of perceptions of impingement, not focusing on perceptions of diversity, aware that ‘space is infinite’, they have been reborn (upagā) in the dimension of infinite space.
6. There are sentient beings that have gone totally beyond the dimension of infinite space. Aware that ‘consciousness is infinite’, they have been reborn (upagā) in the dimension of infinite consciousness.
7. There are sentient beings that have gone totally beyond the dimension of infinite consciousness. Aware that ‘there is nothing at all’, they have been reborn (upagā) in the dimension of nothingness.
The deva (godly) abodes attained with each rupa jhana are listed in AN 4.123, namely, brahmakāyikā, ābhassarā, subhakiṇhā & vehapphalānaṃ.
Now, the above utterance in DN 15 & AN 7.44 omit the 4th jhana or gods of abundant fruit (vehapphalānaṃ) found in AN 4.123. Related to this is AN 9.24, which refers to the 4th jhana as 'non-percipient' (asaññino).
My question is what are the "seven stations of consciousness" supposed to mean (for example, why do the permutations of 'diversity' and 'unity' exist in the various jhana & states of being) and why, in particular, does this utterance omit the 4th jhana?