So that seems cheap, but look at the picture. I'm no electronics guy, but I only see 1 IC on that board, an LM2577, which I think only boosts, not bucks. The picture of it working shows it boosting 12v to 24v.
Is there anything on that board that would suggest to somebody who actually knows what they are doing that this board would also be capable of bucking as well as boosting?
If we look for example at this one instead
it has both an LM2577 to boost and an LM2596 to buck.
Same with this one
both 2577 and 2596.