How to rotate a grouped artworks in the same way as Rotate Tool ?

I have made some code that rotates a grouped artwork.

ASErr rotate( AIArtHandle ah, AIReal radians, AIRealPoint const& center )
{
    ASErr             err = 0;
       
    AIRealMatrix    mtx;
    sAIRealMath->AIRealMatrixSetTranslate   ( &mtx, -center.h, -center.v );
    sAIRealMath->AIRealMatrixConcatRotate   ( &mtx, radians );
    sAIRealMath->AIRealMatrixConcatTranslate( &mtx, center.h, center.v );
       
    err = sAITransformArt->TransformArt( ah, &mtx, 1, kTransformObjects );

    return err;
}

    ..................

    ASErr err = kNoErr;

    //--------------------------------------- ah_selection
    AIArtHandle ah_selection = ..................

    AIRealRect  rect = ..............

    AIRealPoint center;
    center.h = (rect.right+rect.left) / 2;
    center.v = (rect.top+rect.bottom) / 2;

    AIReal  radians = sAIRealMath->DegreeToRadian(30);

    //---------------------------------------
    AIArtHandle     child   = NULL;
    err = sAIArt->GetArtFirstChild(ah_selection, &child);
    err = rotate( child, radians, center );

    while (1)
    {
        err = sAIArt->GetArtSibling(child, &child);

        if ( err || child == NULL)
            break;

        err = rotate( child, radians, center );
    }
    

It works but with one difference. When I select a grouped artworks and apply to it,  it's bounding box does not rotates.

This is same as " Object > Transform > Transform Each" menu way that individual are having their own origin points.

How can I  rotate with bounding box also rotated ?

Thanks in advance.