It would have been nice if the franchise had just elaborated a bit further, either with the Demon Gods and stuff in Heroes or with Zamasu in Super. But they didn't, and at this point probably won't. (I'd love to be proven wrong in the future though, please.)
I don't really know why Mike and them went with the wording the did on the actual translation page. Herms' initial
translation on the forum and the version used in the
Demon Guide are phrased more so that evil Shinjin only go to be with the Makaio and Makaioshin in Makai, with the exact origin of said Makaio and Makaioshin still being unclear.
[spoiler]
Herms wrote:Cosmos
Next is a question on how Toriyama came up with the structure of the DB cosmos. He said it was so that it would be easy for both him and the readers to understand. As he explains, it’s this big ball, divided up into the living world and afterlife, and outside that ball are the Kaioshin.
But, Toriyama adds, at the bottom of that big ball, like an antipode, is the Demon Realm (Makai), where there are the Makaioshin (“Gods of the Kings of the Demon Realm; an obvious counterpart to the Kaioshin), who rule over evil. Toriyama says that it seems at the moment, the Kaioshin’s power is greater than the Makaioshin (Japanese not really having a plural form, it’s unclear from all this whether there is only one Makaioshin or more). To go along with this information, there’s another reprint of the standard picture of the DB cosmos, with labels for the Kaioshin Realm, 4 Kaio Planets, and the Demon Realm. The Demon Realm is labeled as being in that little tip at the bottom of the cosmos, like it was in Daizenshuu 7 (in Daizenshuu 4, where the DB cosmos map was first printed, the Demon Realm wasn’t labeled).
Where Kaio come from
Toriyama is next asked what the Kaio’s heredity system is like. Toriyama explains that inside the giant ball that is the DB cosmos is a world called Planet Kaishin (World-Core), which is where the Kaio are all born and raised. This planet is like a giant version of the Kaio Planets that North Kaio and the others live on. On it is a gigantic tree (or trees; the lack of Japanese plural clouds up things again), the Kaiju (World-Tree), and the Kaio are all born from the fruit of this tree, as Shin-jin (Core-People). The population of this planet is about 80. The Shin-jin are genderless, and their average life expectancy is said to be 75,000 years. They live leisurely lives, studying various things at a school-like castle. But whenever one of the Kaio on the Kaio Planets passes away, they draw lots among themselves to choose who will take that Kaio’s place and become the new Kaio. The Kaioshin, however, are chosen only from among Shin-jin born from a special golden fruit that is particularly rare. Occasionally there are delinquent Shin-jin with evil hearts, and they go to be with the Makaio (“Demon Realm Kings”; apparently the Demon Realm answer to the Kaio, like the Makaioshin are to the Kaioshin, though Toriyama doesn’t explain the term).
So there you have it: the supreme gods of the DB cosmos are chosen by lottery. As Crow T. Robot would say, this is weird theology. There’s a diagram illustrating the whole Kaiju fruit thing, showing South Kaio comes from a normal fruit, and East Kaioshin coming from a golden one. There’s also a picture of North Kaio, remarking on his luck at the lottery, and one of Goku saying he’s surprised Kaio wasn’t chosen for his bad jokes.
Kanzenshuu Demon Guide wrote:According to Toriyama in the 2009 Super Exciting Guide: Character Volume, the Demon Realm is home to the Makaiō (魔界王; “Demon Realm Kings”) and Makaiōshin (魔界王神; “Gods of the Demon Realm Kings”), who rule over evil and are the antitheses of the Kaiō and Kaiōshin. Toriyama does not really say where Makaiō and Makaiōshin come from, only that delinquent members of the Shin-jin (literally “Core People”; the Kaiō and Kaiōshin are members of this race) go to be with the Makaiō and Makaiōshin. It is not clear whether these evil Shin-jin ultimately become Makaiō and Makaiōshin themselves, or if they simply serve as their allies. It is not known how many Makaiō and Makaiōshin there are, though if they are like their good counterparts, there should be five of each. Importantly, it is also unclear whether or not Dabra himself is a Makaiō or Makaiōshin. He is called the king of the Demon Realm (魔界の王/makai no ō), which is what “Makaiō” means, but the terms “Makaiō” and “Makaiōshin” are never used in the series. Also, Toriyama says that currently, the Makaiōshin are weaker than the Kaiōshin, but East Kaiōshin was terrified of Dabra’s strength. It is possible that Dabra is simply a “regular” inhabitant of the Demon Realm who happens to have surpassed the gods who are supposed to be supreme there, similar to how Goku himself eventually surpassed the various regular gods, including Kaiōshin.
[/spoiler]
So while you can headcanon it however you want until they elaborate (if they do), that is all it is. I'd probably err with the notion that evil Shinjin aren't Makaio and Makaioshin, and that we have yet to see one in the franchise. Otherwise it'd have been super easy to label any of the new characters as such in the years since. Even back when the information was first released. Dabra already existed. If he was meant to be a Makaio, he could have been used as an example at that time.