I think we could consider some more factors and techniques than just hugel beds. Though when you are in a dry climate any technique that suggests less need for irrigation might be something to try out i think it isnt necisary to make a holy grail out of building hugel beds. This technique originated in european climates, and even though spain doesnt get much rainfall, and a big part of the country looks like desert, it is in a much higher lattitude. Like some people allready pointed out, that makes up for different natural mechanisms at work.
When in a north african region, or something alike, I personally wouldnt go out all of my way just to build these hugel beds. Part of the system is based on building little hills, not only burying wood. And like Topic starter allready said, sunken beds in stead of raised beds are a much smarter thing in those climates. Also It might be worth while to look more at examples of permaculturalists who have been practicing in similar climates, like geoff lawton was in jordan, and morroco. Luckily australia, the place where permaculture evolved, has very similar climates, and people came up with all kind of solutions and techniques. Like creating shade by planting trees adapted to your region, and so layering your garden (or stacking in space).
Strategies like adding organic matter, not nessicarily wood, but any kind of OM you can find does improve the soil's ability to retain moist and not tilling of the soil also gets way more important the closer to the equator you get. Then there are all kind of techniques like the use of stones and rocks to collect dew can be of great help.
I am not saying not to use buried wood when in north african type regions. If you do have a source for wood it could help a lot, though it stil might be wise to dig even deeper to bury the wood so you can still have sunken bed (with buried wood). The permaculture design manual and other australian recources cóuld be more helpfull when in this climates then sepp's book or patrick whitefields, because they are based on european climates.
And me too, am curiously awaiting results from all you brave desert dwellers who are going to experiment with buried wood.