Lal said: There is no “left-over” kammic energy (in that Brahma bhava) for a Brahma once his lifetime ends.
OK. Now I look at this problem in another way. Maybe the problem is that I had supposed the hetu of both the anariya Brahma realm and the ariya Brahma realm are in the same category.
The rebirth process runs only by Akusala mula PS. So kusala kamma can not be the hetu. And there is no need to cultivate jhana or samapatti to be born in Suddhāvāsā. Because even if Anagami didn’t cultivate jhana or samapatti, if rupa raga samyojana remained, he/she would be born in Suddhāvāsā. So the hetu of the rebirth in the Suddhāvāsā Brahma realm is not equivalent to the hetu of the rebirth in the Anariya Brahma realm.
Suddhāvāsā is inside of samsara. And their manomaya kaya is sankhata. Then, what is the hetu of the rebirth in the Suddhāvāsā Brahma realm? Is it kamma bhava? If so, as a logical consequence, it must belong to rupa kamma bhava. If so again, the difference between the hetu of the rebirth in the Suddhāvāsā Brahma realm and the hetu of the rebirth in the Anariya Brahma realm should be clarified. Because it may mean that a certain rupa bhava can be made in another way without cultivating jhana.