Shader from Unity documentation not work while see only one object on screen

Code from documentation:

 Shader "Debug/Tangents" {
 SubShader {
     Pass {
         Fog { $$anonymous$$ode Off }
         CGPROGRA$$anonymous$$
 
         #pragma vertex vert
         #pragma fragment frag
 
         // vertex input: position, tangent
         struct appdata {
             float4 vertex : POSITION;
             float4 tangent : TANGENT;
         };
 
         struct v2f {
             float4 pos : SV_POSITION;
             fixed4 color : COLOR;
         };
         
         v2f vert (appdata v) {
             v2f o;
             o.pos = mul( UNITY_$$anonymous$$ATRIX_$$anonymous$$VP, v.vertex );
             o.color = v.tangent * 0.5 + 0.5;
             return o;
         }
         
         fixed4 frag (v2f i) : SV_Target { return i.color; }
         ENDCG
     }
 }
 }

One object:

Two objects (just enable second object):

Adding more objects don't change anything.