It is probably a statement related to the average tree. Also, I believe hemp and bamboo are not trees (but I’m also not a plant scientist) so not really relevant in a statement about trees.
I coudn’t find a source for your statement, but I did find that it takes a tree 30-40 years to store a ton of CO2, so maybe that’s what they mean? A tree will store carbon as it grows, because it builds itself with carbon from the air. ecotree.green/en/how-much-co2-does-a-tree-absorb
Sidewalks where I live are bumpy, interrupted by trees, signposts and trash bins and occupied by pedestrians. Much better (and ultimately safer) is to cycle in the middle of the lane to force cars to give you space. You are also more visible that way to cars from sidelanes.