getLayerExtent 获取符号化范围无效？

设置面符号的线宽为80
sym = MBQY_lyr0.symbology
for grp in sym.renderer.groups:
for itm in grp.items:
itm.symbol.size = 80
MBQY_lyr0.symbology = sym
输出范围对比：
print(mf.getLayerExtent(MBQY_lyr0, True, True).XMin,mf.getLayerExtent(MBQY_lyr0, True, True).XMax)
print(mf.getLayerExtent(MBQY_lyr0, True, False).XMin,
mf.getLayerExtent(MBQY_lyr0, True, False).XMax)
结果：
667905.5271032974 668934.9958720704
667905.5271032974 668934.9958720704