DO NOT USE ABOVE ANSWER
Acutally, GetComponentSpaceTransform is not a way to correctly get transform, because it will effect your mesh!!!
You should using:
auto ParentBone2 = SkeletalMeshComponent->GetParentBone(Bone.BoneName);
auto ParentBoneIndex = SkeletalMeshComponent->GetBoneIndex(ParentBone2);
UE_LOG(LogTemp, Warning, TEXT("[jj getpose] parent: %s "), *ParentBone2.ToString());
auto WorldToParentBone = SkeletalMeshComponent->GetBoneTransform(ParentBoneIndex).GetRotation();