It might depend on which miller it is from? Certainly, I know at one point, the buckwheat flour I was buying was much heavier, and didn't work for some of my dishes. But it is also why I cut it 1:1 with the lighter flour, rather than my usual 2 parts buckwheat to 1 part (or less) of other.

Also, for a long time, it was the one readily accessible flour that wasn't really just starch, so I used it for everything.