You've just contradicted yourself by saying that an area can only be trained overall while also acknowledging "emphasis". It can't be both.
In effect, he and you are confusing one issue with another, something commonly done BTW. The thread wasn't about physiology and the structure of the muscle. The structure of a muscle has nothing to do with targeting different sections of it. This is confusing to some here and many elsewhere.
Off course you can emphasize a certain part, chest has got three parts,
pectoralis major sternal, clavicular and pectoralis minor.
They all are activated if your training, but by changing the corner you can emphasize a certain part.
The TS is talking about a cleavage at the sternum, that is genetically determed cause it has got nothing to do with the actual muscle but with the tendons. Short tendons, nice cleavage,
with shitty tendons you have to have a hell of a chest to compensate that.
Increase the size of your chest by using other methods like increasing your ROM, heavy cables, prefarably on a bench and/or dumbells.
Also bring down your fat and you will see you muscles and maybe have a nice cleavage.