When those trees die and then rot or burn, that CO2 will be released right back into the atmosphere. They’ll temporarily hold some, yeah, but it’s like trying to rapidly fire a squirt gun at a fire when someone else is spraying it with a firehose of gasoline.
Especially because trees plant themselves. If they want to set aside the land for forest and seed it a little to get going - great - but those large tree planting operations are a waste of time at best or carbon credit loopholes at worst.