I cannot read that, I just can't even click on the link, sorry.
FWIW I hate wearing flat shoes because I feel so short, small and unempowered. I am 5ft7, and have size 8 feet so am not really short but I feel it.
This applies to flat boots as well. I think it's because I spend nearly all the time in very chunky boots with about an inch or so heel, rather than being sleek and groomed and 'feminine' they are often men's boots as well so I feel kind of strong in them.
I dislike wearing heels, very uncomfortable and awkward. So 'daring' to wear flat shoes would be daring to feel unempowered, for me - it depends how you classify 'flat' though.