What is expected: A shader with all the same properyu names as Unity Standard would have the associated values get mapped correctly when shaders are blocked.
What happens: Not all are properly passed on, such as _MetallicGlossMap and _SpecGlossMap, when shaders are blocked, resulting in an incorrect material configuration.
Here is a list of the main inputs for the unity standard shader included with unity 2018.4.20
half4 _Color;
half _Cutoff;
sampler2D _MainTex;
float4 _MainTex_ST;
sampler2D _DetailAlbedoMap;
float4 _DetailAlbedoMap_ST;
sampler2D _BumpMap;
half _BumpScale;
sampler2D _DetailMask;
sampler2D _DetailNormalMap;
half _DetailNormalMapScale;
sampler2D _SpecGlossMap;
sampler2D _MetallicGlossMap;
half _Metallic;
float _Glossiness;
float _GlossMapScale;
sampler2D _OcclusionMap;
half _OcclusionStrength;
sampler2D _ParallaxMap;
half _Parallax;
half _UVSec;
half4 _EmissionColor;
sampler2D _EmissionMap;
If present in a blocked shader these should be mapped to Unity Standard.