Glslang doesn't build spv code with RelaxedPrecision

[Nelonn]

I'm using pair of glslang and SPIRV-Cross and compiling simple shader to ES target without optimizer. Input code:

#version 450 core

precision mediump float;

layout(set = 0, binding = 1) uniform mediump sampler2D sTexture;

layout(location = 0) in VertexData {
    vec4 Color;
    vec2 UV;
} In;

layout(location = 0) out mediump vec4 fColor;

void main() {
    fColor = In.Color * texture(sTexture, In.UV.st);
}

Without any modifications im getting output:

#version 300 es
precision mediump float;
precision highp int;

uniform highp sampler2D sTexture;

layout(location = 0) out highp vec4 fColor;
in highp vec4 In_Color;
in highp vec2 In_UV;

void main()
{
    fColor = In_Color * texture(sTexture, In_UV);
}

If I modify GlslangToSpv.cpp with manually forcing precision to RelaxedPrecision

spv::Decoration TranslatePrecisionDecoration(const glslang::TType& type)
{
    return spv::Decoration::RelaxedPrecision;
    //return TranslatePrecisionDecoration(type.getQualifier().precision);
}

Then im getting following output:

#version 300 es
precision mediump float;
precision highp int;

uniform mediump sampler2D sTexture;

layout(location = 0) out vec4 fColor;
in vec4 In_Color;
in vec2 In_UV;

void main()
{
    vec4 _19 = In_Color;
    highp vec4 hp_copy_19 = _19;
    vec4 _29 = texture(sTexture, In_UV);
    highp vec4 hp_copy_29 = _29;
    fColor = hp_copy_19 * hp_copy_29;
}

What's the problem, why does it constantly generate highp without forcing? It's clear that I can't use this modification because it affects other places like uniforms, etc.

[Nelonn]

DXC does all great, if I use min16float on cross GLSL I got mediump