i'm a bit late as well, but only just heard about and got interested in rocket stoves, dunno if they are good or bad, work or otherwise, need more info' and need info on building one, apparently the ones they sell burn too fast and cost too much.
suppose one might use anything at the bottom of a new garden, can't realy say if that is hugelkultur or not, this is what can happen when a new catch cry hits the scene, is it or is it not? we hide bricks, broken tiles and cement under teh garden.
look at our bale garden presentation did we use hugelkultur before hugelkultur became?
i would say ye, and now with our new beds (corrugated roofing sides) we use hugelkultur because we have teh remains of trees to recycle.
we find in gardening we do what suits us, if it has a anme so be it, to use it simply makes common sense to do waht we do.