Learn English – Why does Richard Stallman refer to random strangers with feminine pronouns

For those of you who don't know Richard Stallman, he's the founder of the Free Software Foundation and the father of the Free Software movement in general.

I read a lot of his writings, as well as watch his videos, I even had the pleasure to attend one of his speeches about a month ago. There's one thing I noticed: whenever he mentions someone else without specifying the gender, he always uses the feminine pronouns.

Explicit examples are not easy to search for, I'm posting them as soon as possible:

• "[…] After I sang it, someone else in the room said […] She said, […]"

  https://www.gnu.org/music/writing-fs-song.html

• "[…] I was taken to an office, introduced to a lawyer […] She didn't really dig much […]"

  https://stallman.org/genoa-experience.html

• "About half the time, the beggar accepts this offer. […] I invite her to choose the food, […]"

  https://stallman.org/articles/responding-to-beggars.html

• "She said it was a binder 3,000 pages long […]"

  https://stallman.org/articles/asked_to_lie.html

• "At dinner at a Japanese restaurant, the person next to me said she wanted to work with abused children. […]"

  https://stallman.org/jokes.html

• "A friend once asked me to watch a video with her that she was going to display on her computer using Netflix. […]"

  https://stallman.org/stallman-computing.html

• "Another tourist in the group offered me her arm to hold on to so I could continue walking […]"

  https://stallman.org/articles/tikal.html

I thought of a few possible ways to explain it:

• it's a contracted version of "he/she" or "s/he" (however he seems to be the only one who uses it)
• there's some grammar construct I'm not aware of, similar to the feminine third person in Italian (again, I don't know of anybody else using it in English).

Is he just using some polite version?