Which units are considered "flat-chested"?

Which units are considered "flat-chested"? - Modern trendy kitchen interior with dark cabinets and counter in spacious contemporary flat

There are at least 2 game mechanics I know which only apply to "flat-chested" units (the Flatty Squad and the Anti-Flat Chest evility). Looking around the Internet I found a few examples, interesting anomalies and educated guesses, but no complete list of all classes and unique characters which are considered "flat-chested" in the context of these mechanics.

I am playing the PC version, if it matters.






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Which units are considered "flat-chested"? - Modern bathroom interior with freestanding tub
Which units are considered "flat-chested"? - Contemporary kitchen with stylish empty furniture
Which units are considered "flat-chested"? - Contemporary kitchen interior design with empty dark furniture and decorative vases and plants





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