According to this site, body press increases its damage based on the users defence but doesnt explain what that means exactaly. Does that mean it uses the defence stat instead of the attack stat when calculating damage? Does it mean it adds a multiplier based on defence? I'd really like to know. (Also if someone could make the body-press tag a thing that would be great)
According to Smogon, Body Press uses the user’s defense stat instead of the attack stat during damage calculation.
The user attacks by slamming its body into the target. The higher the user's Defense, the more damage it can inflict on the target.
Higher defense = higher base power.