Something tells me those houses won't stand up to even mild earthquakes.

Are poverty-stricken areas going to have the electricity needed to run this machine? And a few weeks per house seems awfully slow. Seems to me you can build a house with adobe bricks or rammed earth construction in less time and with readily available labor. I would also guess this 3D printed material is lower density than the older alternatives, so it wouldn't be as resistant to weathering.

Exterior surface improvements would extend weathering. A truck mounted operation would include its own generator or solar panels and batteries. Speed will improve as the tech matures. The demo was proof of concept not prototype.

I'm sure that people could build mud shelters by hand a lot quicker than two days. The mud may be good for walls, what will the roof be made of? Mud is not known for being particularly resistant to rain.
Also, as has been said, poverty stricken areas are less likely to have electricity to operate the machine, so a generator and fuel would be required. If a generator and fuel was available, the area probably wouldn't be 'poverty stricken.
This seems to be a 'rich kids' solution, looking for a problem.

I imagine the biggest difficulty will be getting the consistency of the building material right so that it has just the right amount of water content. Too dry and it will crumble, too wet and it will sag. Either way will almost certainly lead to a poorly built house, with obvious results.

Printed mud construction would be similar to layered mud, which isn't as strong as rammed earth construction or reinforced mud housing. Also if a roof and outer coating have to be applied after 2 weeks of printing then the unit's not really made from a 3D printer rather a portion of it is made from a 3D printer. Still needs windows and a door at minimum and most people want electricity, water and floors . This would work well for making defense walls, storage units or garages but at the moment this is a bit slow, insubstantial and untested for housing.

Somebody should combine this process with "Hempcrete" and maybe hit a homerun. They could use the "Mud" for the structural portion of the house and then use "Hempcrete" to fill in the walls.

"...in developing regions where traditional forms of construction might not be possible..." This mud printer needs power just as "traditional construction". The mud mixture must be prepared by sifting and combining sand, clay, cement, and water. This makes up much of the labor and cost of earthen construction. The expertise to build with earth is simple and easy to teach, but not necessary in most developing regions because it has been used for centuries. Earthen structures can be stable and last centuries. Earth is by far the most cost effective material in developing regions but no high tech is needed to utilize it.

Mass produce, must for India & Africa & Asia alone

Add chopped straw for reinforcement, especially if some can be made to partially stick out so subsequent layers will bond. 3D printing like this would essentially be a high tech version of a cob wall.
Cob construction is basically lumps of earth and clay with fiber, often straw or dried grass plus herbivore manure, piled up by firmly smacking cobs (lumps) of the material together.
In the areas where such buildings would be constructed, there are likely local experts in making and applying various types of earthen plaster.