Uncorrect normals tri-planer shader

I'm making a tri-planer shader that can accept a texture atlases for images and their normal maps. I got it working for showing the textures, but the normals are being set incorrectly: screenshot

The cube to the left is my shader, the one to the right is the legacy BumpedDiffuse.

The shader is heavily based on example 1-3 from section 1.5 of https://developer.nvidia.com/gpugems/GPUGems3/gpugems3_ch01.html

 Shader "Custom/TriPlaner" {
   Properties {
         _Atlas ("Texture Atlas", 2D) = "white" {}
         _NormalAtlas("Normal Altas", 2D) = "bump" {}
     }
     
     SubShader {
         Tags {
             "Queue"="Geometry"
             "IgnoreProjector"="False"
             "RenderType"="Opaque"
         }
  
         Cull Back
         ZWrite On
         
         CGPROGRAM
         #pragma surface surf Standard fullforwardshadows
         #pragma exclude_renderers flash
  
         sampler2D _Atlas;
         sampler2D _NormalAtlas;
         
         struct Input {
             float3 worldPos;
             float2 uv_Atlas;
             float2 uv_NormalAtlas;
             float3 WorldNormal;
             INTERNAL_DATA
         };
             
         void surf (Input IN, inout SurfaceOutputStandard o) {
             float3 blend_weights = abs(IN.WorldNormal);
             blend_weights = (blend_weights - 0.2) * 7;
             blend_weights = max(blend_weights, 0);
             blend_weights /= (blend_weights.x + blend_weights.y + blend_weights.z).xxx;
 
             float4 colFetch = tex2D(_Atlas, IN.uv_Atlas);
 
             float2 bumpFetch = UnpackNormal(tex2D(_NormalAtlas, IN.uv_NormalAtlas)).xy - 0.5;
 
             float3 bump1 = float3(0, bumpFetch.x, bumpFetch.y);
             float3 bump2 = float3(bumpFetch.y, 0, bumpFetch.x);
             float3 bump3 = float3(bumpFetch.x, bumpFetch.y, 0);
 
             float4 blend_color = colFetch.xyzw * blend_weights.xxxx +
                                  colFetch.xyzw * blend_weights.yyyy +
                                  colFetch.xyzw * blend_weights.zzzz;
             float3 blended_bump_vec = bump1.xyz * blend_weights.xxx +
                                       bump2.xyz * blend_weights.yyy +
                                       bump3.xyz * blend_weights.zzz;
             o.Albedo = blend_color.xyz;
             o.Alpha = blend_color.w;
             o.Normal = blended_bump_vec;
         } 
         ENDCG
     }
     Fallback "Diffuse"
 }