The surface are to mass ratio is much higher on pellets. On hunks, there's an interior that gets exposed to higher and higher temperatures, but is not burning; or better said, not being exposed to oxygen and combusting. That can't happen in pellets. So I think a lot of flavor-laden gasses are given off instead of burning immediately. Some may also burn, but will make different combustion chemicals than just the wood itself. Sometimes you can see the sap running out, and hear the gasses escaping. Pellets just don't do that; there's no interior to "cook". They burn up immediately, IF any of them are left after the pellets are compressed. And then when it does burn to that layer, it's now a very dry substance, more closely akin to a pellet burning. Perhaps at a different temperature, because those combustible gasses and some sap components certainly add a little to the heat produced, already gone when small pieces are burned. Same amount of heat, probably, but a different process.

Different compounds burning at different times yields different flavor. You want burning wood hunk flavor, you have to burn wood hunks somehow. The way this smoker incorporates hunks does look like a good idea. Doing it in other pellet smoker is more of a challenge. One guy said he lays his smoke tube on a small slab of wood, which gets it going some without having to be right up against the burner chamber; I'm going to try that next in my ZGrill.