It's armor, so we're going for more protection. Other considerations like flexibility and whatnot is getting too far into the weeds. And as a reminder, it's not supposed to be a historical progression through the timeline either. Several of these cultures are depicted compressed into a representation of about a century of time. Several decades in the least.  So, for body armor, which is supposed to give a +1 hack resistance for each tech up the ladder, going from a bell cuirass to an exomis, which is the historical progression, is not intuitive to its effect. During Sparta's height, sure, most Spartiates wore the exomis instead of a cuirass or linothorax, but they had the technology and knowledge of those things and they were available and some of them wore the heavier items, so they make sense as techs. 

Well, I don't think Farmstead techs or Arrow techs at the Forge follow a light->heavy progression for example, but a worse->better one. In the case of armour, I streamlined things now merging increased "mobility" and slight "resistance" decrease with an overall "defence" increase, along with cheaper costs, thus worse->better in many respects. Realistically, it's hard to talk about progression regarding armour, since their use overlapped a lot, but one can talk about when they started to be adopted more often. Also, only considering a Linothorax progression would be too made up, since we know very little about it in the first place (EDIT: but I remember thinking about if using a couple of Linothorakes types, have to look into it better, but for sure I wouldn't put Bronze Cuirasses after them).

This is fantastic! I'll add it.   Well, I'm down foe making a more realistic 'progression', but you gotta remember that the 'progression' in the game should be from light -> medium -> heavy. That's a general trend throughout the game for many types of tech progressions. Like how it goes from baskets -> wheelbarrows -> large carts. I know this particular example is problematic too, but it's illustrative of the concept and its pitfalls.  In your example, going from patina bronze cuirass -> different looking bronze cuirass -> different looking bronze cuirass -> iron thorax isn't an intuitive progression. Some Spartans certainly used the linothorax at some point, so it seems a better progression to go with: Quilted Linen Corselets -> Laminated Tube-and-Yoke Corselets (Linothorakes) -> Bronze Cuirasses (Chalkthorakes) or something like this. Or Linothorakes -> Scale-Reinforced Linothorakes -> Bronze Cuirasses. Not sure myself. Several directions which can be taken.  ->  -> 

Three versions ago? Maybe? Supposedly? It was communicated then. I never paid attention to it, but I believe @guerringuerrin.