What a fascinating article on this growing area of voice training.
I am struck by how flexible everyone's speaking and singing voices can be. We often end up vocally drawn to what Estil trainers call our Attractor State. So we are attracted to the way we sound through force of anatomical or cultural habit, or because we define ourselves through our voices a certain way. These two videos shows how all our voices are capable of a much wider range of sound than we mostly use. As a musician, I see this most often with regard to musical styles. People say 'I am a bass', 'I only sing opera', or 'I love to belt', when actually that is just their comfort zone. The same applies to gender.
Also, a point about gender binaries. My experience is that people of all genders have both high and low voices, and there is a continuum of everything in between. Also, people use a range of voices in different emotional contexts. These speakers chose, or were pointed towards, new voice pitch and resonance that is significantly different from their initial sound. This feels like an unnecessarily narrow view of the 'feminine' to me, a vocal gender binary. Fluidity can be a so much better (and more practical) place to start from. In both cases, the higher pitch seemed comfortable to the speakers, which is the main thing.