关于Show的一个奇怪现象

um=4;
list=Table[ParametricPlot3D[{Cos[u]+n/2,Sin[u]+n/2,v},
{v,0,1},{u,0,um},Axes->False,Boxed->False,
PlotStyle->Directive[FaceForm[Green,Texture["ABCDEFG"]]],
TextureCoordinateFunction->({2#5,#4}&),Lighting->"Neutral",
Mesh->None,PlotRange->All,ViewPoint->{-30,10,20},
ViewAngle->.025],{n,0,2}]
Show[list[[1 ;; 3]]]