But not necessarily released as CO2, which is what "re-emitted" means to me. If it goes atmosphere -> tree -> fungus -> bits of fungus buried in the ground for millions of years, that's effective sequestration.
It may well be, but that's not what happens to most of the wood in trees— most of it rots (CO2 released slowly by the organisms consuming the wood) or burns (CO2 released by combustion).