Well it can be sunk in some other ways but those trees were already doing it before they got logged. The most efficient way of CO2 sink is the one that's already there because it takes no resources to keep it.
If you burn it for fuel though, it's back in the atmosphere.
Please note that I am NOT advocating that we log old-growth forests, just that the carbon math isn't simple or, well, clear-cut.
I'm guessing it probably varies by species and soil and climate and such. It's not a given that old growth will keep sequestering more than replanted forest. Old growth, according to that followup study, eventually reaches a carbon equilibrium. They don't grow to infinity and keep sucking up carbon. If you take those trees and move them into furniture you've essentially freed up soil and canopy (light) for more wood to grow.
If they just replace the old growth with rangeland or development, then yes, it's much worse.