They might want to write that into their books, but note that by buying an existing forest, no additional CO2 reduction is achieved on a global scale.
I know it's counter-intuitive, but it's *almost* better for the environment to NOT recycle paper and bury it in landfills. We're essentially reversing the process of extracting oil.
At best, a young and growing forest can be a temporary carbon sink, until it reaches maturity (and steady state).
Alternatively, a forest might support continual carbon sinking if and only if the recently dead and/or mature trees were somehow harvested and treated/stored in such a way that their carbon would not decompose and re-enter the rest of the biosphere.
The only thing comparable these days is peat bogs that act as carbon sinks (because their plant matter does not decompose due to acidic and anaerobic environment).
A growing forest does consume CO2 more than it releases, but it does not seem to be the case now
A forest that is left untouched acts as a CO2 sink by photosynthesis and "capturing" the CO2 as bio-mass.
A re-forestation of land previously used for agriculture acts as a bigger CO2 sink because the potential for biomass capture is greater there.