Why GetComponentSpaceTransform`s result is different from GetMesh()->GetSocketTransform?

Development Programming & Scripting C++
1

While Im writing an animation node, I find that these two functions result is different:
FTransform t2 = AnimInstance->Character->GetMesh()->GetSocketTransform(“Bip001-L-Forearm”, ERelativeTransformSpace::RTS_Component);
FTransform t3 = Output.Pose.GetComponentSpaceTransform(LeftForeArmBone.GetCompactPoseIndex(BoneContainer));

2

I know, but I am not gnna tell you