True, I could see a society that's not hetero-normative "catching" transgendered children at a younger age. But even in a society that is intellectually accepting of transgendered and homosexual people, they still have to deal with the fact that they are "not like the other little boys/girls". Which will cause some children, especially children raised to believe in obedience and structure, to suppress and hide things like that.
which leads me to my original point. Does a transgendered Qunari, who comes to that undertsgtanding after the age of 12, get told "too bad, so sad" or do they get told "We know the Qun is Certainty and all, but respecting gender identity is Waaay more important. Here's a sword."
The answer to that can't be "The Tamassrans always identify them before that."
I don't know, obviously, but I don't see why the answer to that can't be: 1) Either your role is re-assigned based on the premise that you were given the wrong role to begin with or 2) You are re-educated. I imagine which happens depends on a variety of factors, especially whether it had the potential to cause rebellion or disruption to the Qun. The assumption that Qunari have no flexibility or judgment comes with the initial exposure to it being mainly soldiers (who would naturally be given little to no flexibility or judgment, for their own good, as it doesn't suit their role - this explains Sten). I see no reason to assume the Tamassarans truly have no flexibility or judgment, since that's essentially a part of their role. I would also say I imagine it happens rarely if they are any good at assigning roles.
Also, I think 12 is low-balling it with age, though I do appreciate the parallelism to The Giver, which is very much how I see this "Society picks your job" aspect of the Qunari. I don't see why the role has to be established quite that young or that we've been given any indication at what age it is assigned. We have also seen that the role can be "adjusted" if not completely re-assigned (no, we haven't seen a baker become a soldier or anything, but we have seen roles change within a specific job.
There do seem to be "changes" in the Qun (though I don't think the transgender/Krem thing is one of them, as it perfectly fits with Sten asking how you can lead as a woman - in fact, I swear, he asks if you ARE a woman at one point as though he's confused). But as Vivienne says about the Circle, people have different experiences even in the same place. It's entirely possible Bull and Sten both came away with differing views of the Qun. I know we're meant to believe Qunari are these cookie-cutter, identical creatures, but, honestly, that is impossible. I'm sure they have a harmony to their society and a sameness - that seems inherent and crucial to the Qunari - but that doesn't mean they would explain every instance the same way. I don't see any change that couldn't be explained this way. The biggest change seems to be in how children were raised. IB's sounds far more likely than Sten's to me - since even Sten specifically says there are ALL kinds of roles, even musicians/bards in Qunari society. I see no reason to "disbelieve" Sten, but I see plenty of reason to consider he may be assimilating his experiences to everyone in a way that isn't as true under the Qun as he thinks it is.