There's an actual explanation in the original article about some of the wardrobe choices. It's even dumber, and it involves effective altruism.

It is a very cold home. It’s early March, and within 20 minutes of being here the tips of some of my fingers have turned white. This, they explain, is part of living their values: as effective altruists, they give everything they can spare to charity (their charities). “Any pointless indulgence, like heating the house in the winter, we try to avoid if we can find other solutions,” says Malcolm. This explains Simone’s clothing: her normal winterwear is cheap, high-quality snowsuits she buys online from Russia, but she can’t fit into them now, so she’s currently dressing in the clothes pregnant women wore in a time before central heating: a drawstring-necked chemise on top of warm underlayers, a thick black apron, and a modified corset she found on Etsy. She assures me she is not a tradwife. “I’m not dressing trad now because we’re into trad, because before I was dressing like a Russian Bond villain. We do what’s practical.”