I looked into Worldstove and the Beaner in particular in some greater depth. After jumping around at their site, I might characterize them as a "Green Innovation" company that happens to have a sideline in backpacking stoves.
Based on the degree of seriousness I see manifested on that site, I'd expect that these Beaner stoves do indeed produce biochar, because that is one of their main goals.
They want users, particularly in poor communities around the world, to be able to use their stoves to get greater cooking efficiency out of biomass, and then be able to use the cooking byproduct (biochar) to enrich the earth in their community, which in turn makes the production of stove-usable biomass easier.
It's a great idea, and considering that their point of entry into this is the production of biochar and biomass fuel efficiency, I would be quite surprised if the stove isn't producing biochar as advertised (as well as being relatively efficient).
In a video on their YouTube channel, the inventor says that 100g of biomass cooks for 22 mins and generates 30-40g of biochar.
That's pretty awesome.