Why do programmatically generated textures behave differently than manually added textures when used as Terrain splats?

When I add programmatically generated textures versus manually added textures (jpeg files added through the inspector) as splats to my Terrain object they disappear from view when I am viewing the terrain close up. The textures are each 1x1 pixel. The manually added textures derived from the jpeg files work fine regardless of distance.

   public SplatData[] Splats;
   public boolean useManualSplat = true;

   void BuildSplats(TerrainData terrainData){
     if (useManualSplat) {
       SplatPrototype[] splatPrototypes = new SplatPrototype[ Splats.Length ];
       for (int i = 0; i < Splats.Length; i++){
         splatPrototypes[i] = new SplatPrototype();
         splatPrototypes[i].texture = Splats[i].Texture;
         splatPrototypes[i].tileSize = new Vector2(Splats[i].Size, Splats[i].Size);
       }
       terrainData.splatPrototypes = splatPrototypes;
     } else {
       SplatPrototype[] splatPrototypes = new SplatPrototype[ 2 ];
 
       splatPrototypes [0] = new SplatPrototype ();
       splatPrototypes[0].texture = new Texture2D(2,2);
       splatPrototypes [0].texture.Apply ();
       SetSplatColor (splatPrototypes[0].texture, Color.red);
       splatPrototypes [0].tileSize = new Vector2 (100f, 100f);
 
       splatPrototypes [1] = new SplatPrototype ();
       splatPrototypes[1].texture = new Texture2D(2,2);
       splatPrototypes [1].texture.Apply ();
       SetSplatColor (splatPrototypes[1].texture, Color.red);
       splatPrototypes [1].tileSize = new Vector2 (100f, 100f);
     }
   }

   void SetSplatColor(Texture2D splat, Color c){
     for (int i = 0; i < splat.width; i++) {
       for (int j = 0; j < splat.height; j++) {
         splat.SetPixel (i, j, c);
       }
     }
   }

Programmatic textures used as splats... note the grey/default color is too close and therefore the textures (red/green) are not drawn. If I zoom out more of the terrain is colored and if I zoom in non of it will be colored:

Manually added jpeg derived splats... red/green color is visible from any distance:

I am very curious what makes the textures different so that I can use programmatic textures and to improve my understanding of the Unity's rendering process.