From what I've seen, claims to this effect often turn out to be false. For instance, from https://billmckibben.substack.com/p/a-little-xmas-cheer-for-...:
> ...the world’s largest supplier of wood pellets for power generation ... has long insisted that it doesn’t use big, whole trees, but only uses wood waste, “tops, limbs, thinnings, and/or low-value smaller trees.” It insists it only sources wood from areas where trees will be regrown, and that it doesn’t contribute to deforestation.
> As it turns out, Mongabay reporter Justin Catanoso found a management whistleblower who pointed him in the direction of clearcuts that the company was making: Catanoso watched as a feller-buncher machine grappled down a fifty-acre forest and fed the old oaks straight into a chipper, producing tons of wood to be turned into pellets. The whistleblower said that was par for the course: “We take giant, whole trees. We don’t care where they come from. The notion of sustainably managed forests is nonsense. We can’t get wood into the mills fast enough.”
> He continued: “The company says that we use mostly waste like branches, treetops and debris to make pellets. What a joke. We use 100% whole trees in our pellets. We hardly use any waste. Pellet density is critical. You get that from whole trees, not junk.”