It just makes one unable to take falling damage, aka creates an air cushion, it does not allow one to float forward or proceed downwards in a controlled manner. It keeps one falling slowly enough that they won't get hurt upon hitting the ground, but it also doesn't cancel out other forces pushing the character around. So, theoretically, it could be used to glide very inefficiently.
DG has no STR score. At no point has it ever had a STR score. At no point will it ever have a STR score.
Body is the physical stat, a rough equivalent in some respects but much more abstract in that it accounts for physical strength and physical agility at the same time, with how much of each dependent on backstory and various other bits on the character sheet. 10 is the rough equivalent to human average. Can the average human climb a tree? Probably, if the branches are aligned well. Can the average human jump from tree to tree? Probably not, but it's possible for someone naturally acrobatic or who has trained to do such a thing... Like someone with a decent Body stat who is trained as an acrobatic fighter. A character could have 100 Body, and if they're fluffed as a brick in full plate armor who waddles around whacking things with a stick, they aren't going to be climbing anything or jumping off of anything and landing on anything but the ground. One could even get away with some nerd with like 10-20 Body jumping around in trees if it made sense in the context of the character's history.