Walipinis originated in the Andean high desert. That's a very dry climate, so if you live in a wetter area you would need to modify the design in a way that would help with wall stability. That said, sunken earth greenhouses aren't limited to dry climates.
Winter photosynthesis: Eliot Coleman lays out nicely how to calculate how many "grow" days you would actually have over the winter based on available sunlight. It's in his Winter Harvest Handbook, (note the use of the word "harvest", rather than "grow"). Where I am at about 42 degrees latitude, Nov. 10th - Feb 10th or so are non-grow days. Just not enough light. The trick is to time planting in late summer so that you're harvesting mature greens over the winter, and letting smaller/younger plants overwinter to be ready for growth in spring.
Those of you in warmer climes/closer to the equator have a shorter no-grow light season, obviously.