Hi! Huge lore nerd here, I might be able to help explain! (I do not mean that in an asshole way I genuinely want to help explain why this might be)
What I think (and I could be wrong, I donāt know what fics you read) the reason this is often mentioned has to do Jamils position and how genuinely horrific his situation is, and some context clues we can take from both his OB flashback, lines in the Japanese, and other dialogue.
On that note, its also a result of associating how fucked up the Asims (not Kalim) are with the entirety of the Scalding Sands, which doesnāt make alot of sense until you realize that in theory, whatever legal system they have either allows or permits this, or there is an extreme case of corruption going on.
Back to Jamil, In the English Dub, for some unknown reason, Jamil is referred to as an indentured servant, which makes things more confusing, considering how indentured servants actually work. (Forced to work for free until either a debt is considered paid or for a contracted certain time period, although historically excuses and situations would be manipulated often to extend this), but in the Japanese original, he is referred to as a slave.
In either form, if we draw from his parents reaction to even the concept of Jamil surpassing Kalim in anyway, his stated inability to leave the Asims, and the fact he is practically treated like a meat shield for Kalim, and cross compare that to the historical treatment of both indentured servants and slaves, it becomes clear that its not too different.
From there, the conclusion can easily be drawn that if Jamil is to āoverstepā in the eyes of the Head of the Asims (not Kalim, his father), it would likely end violently, not just for Jamil, but possibly his whole family too.
Although this doesnāt necessarily mean execution or dungeons, beating or torture is unfortunately another possibility.
Itās very, very clear that the Asims, outside of Kalim, are not good people, and Kalim, as we already know, can be quite the unreliable narrator when it comes to directly addressing the horrors and atrocities committed by his family, even those done to him directly (Kidnapping, attempted murder, assassinations, etc) both as a way to cope, and because he literally grew up knowing nothing else than that life. That was his norm.
Jamil has also been used as both a poison tester and bodyguard since youth. They directly used a child, hell, someone elses child, as a shield and caretaker for him.
In their eyes, he is more of a tool than a human being. He is dehumanized to the point of them seeing his life as practically having only worth if heās serving and protecting Kalims.
When he was poisoned as a child from testing Kalims curry, if not for Kalims intervention and desperation to save him, they would have most likely allowed him to simply die then and there, and shrugged off his death as the loss of an asset, and nothing more than.
So, if one thinks about it, the Asim riches are theoretically made of the blood and suffering of those in their grasp.
Now, in a normal situation, Iād imagine the Asims would be on every news station if just the concept of them even having slaves got out, not to mention the horrific treatment. But heres the thing : We know that the Asims hold high government power, and are quite literally direct relatives to the royal family.
So we can theorize that, to get away with such disgusting blatant abuse and dehumanization, the Scalding Sands either legally permits this treatment, or the corruption within its government runs deep and rampant enough for them to get away with it in the first place.
Personally, I believe the latter. It would clear up the reason as to why they are permitted to go to schools / have an education, aswell as friends and some basic communication outside, (although we do know it is monitored/ they are restricted from saying certain things) This may be possibly usrd as a way to make the situation and treatment seem less fucked than it is, and to make the general public more complicit in allowing this to continue.
But anyway, thats really just my deductions from what Iāve gathered, although the Scalding Sands doesnāt seem to be the only country with suspicious and/or neglectful or possibly corrupt behaviors, as I could go on another long discussion of the Sunset Savannas obvious case of the lower class neglection and my own theories of illegal citizen displacement for profit because the sheer existence of the āhot springsā MAKES NO SENSE UNLESS THATS THE CASE-
*ahem* Sorry. Anyway. We also know that Briar Valley suffers double extreme cases of racism (or specism?) with both humans, and as shown in (SPOILERS) Lilias dream, some fae aswell, as they are considered lower or literally ādirtyā and ācontaminatedā, which we can gather is also extreme from the way they treated Lilia after even after he loyally served and protected the country for hundreds of years not to mention SACRIFICED HIS LIFE FORCE to hatch their dying prince. Ontop of that, we see a significant overstepping and damn near usurption of power with the Senate.
So it really isnāt just the Scalding Sands that has these issues, I think itās just more prominently brought up since Jamils and Kalims story is pretty directly centered around it.
Sorry if that was a huge yappathon. I really hope this helps clear up any confusion you may have and if you have any questions let me know!!
Have an awesome day/night!
(Once again I genuinely mean this to be helpful I am not trying to be rude in any way ;ā;)