The conclusions sound pretty much the same as those on wearing regular shoes vs. zero drop minimalist shoes (or none at all). Support a piece of your body for a long time and it gets soft and/or weak. Breasts, ankles, arches...
I'd love to know what his data said about much larger breasts - surely there a point where bras were advantageous. Or did he focus on the perky smaller ones? What a job...
He might also have just gone to study one of those African or Amazon tribes where women never wear bras.