could the clones have been modified or possibly brainwashed into obedience and acceptance of their fate?
Aside from this not being mentioned anywhere, even if that's the case, the greater freedom they have when adults (before the harvesting starts) doesn't make much sense.
If you were in charge of breeding and raising clones, wouldn't you be concerned that the clones might come into contact with normal people, or media, that makes them question their fate?
Wouldn't you be concerned that at least some of them might start wondering why other people get to live to a ripe old age, or get curious about trying risky (from a might damage the organs point of view) activities like drink and drugs and sex and so on? Or get depressed about the whole thing and start self harming?
Or even concerns that the clones might catch contagious diseases? I mean, if you've gone to all the trouble of cloning them in the first place, it's a waste of effort if you let them wander around in public and they then catch some nasty contagious disease that might kill them before they've had a chance to donate their organs for the greater good
And what about the general public's attitude? Think about animal rights activists, for example, and the campaigning they do about not testing drugs etc on animals. It's not unheard of for animal rights activists who feel extremely strongly about the issue to resort to violent tactics in attempts to shut down animal testing. Is it really conceivable that no one at all would object to sentient clones being bred for organ donation, or that any objections would be limited to nothing more direct than a few letters to MPs / newspapers?
So even if the clones are brainwashed or whatever (and I agree it's shoddy writing to not mention it if that's supposed to be the case), I don't think it's likely that all the population would be in complete agreement that harvesting the clone's organs would be just fine. Especially if the adult clones are out and about, where they might meet the general public and form friendships or acquaintances, or even just get the public thinking uncomfortable thoughts about the clones seeming just like ordinary people.
Surely there'd be a real risk of normal people developing moral objections to harvesting clones, or people already with strong moral objections, who would attempt to rescue / unbrainwash clones wandering about in public?
It just doesn't hang together properly for me.