IOS release, UV precision

**Case:**
model uv precision: 0.0001

**Result:**
IOS debug: ok;
IOS release: bad;
IOS relase and option(FILAMENT_DISABLE_MATOPT "Disable material optimizations" ON): ok;

**Posible Cause**
float3->half3 by auto optimzation of shader(constructed from base.mat.in);

**Question**
However, if I force to set precision in following mat, it not works. GPU frame capture still show float3->half3. Why is that?
file: base.mat.in
`fragment {
precision highp float;
void material(inout MaterialInputs material) {}
}`

related:
https://github.com/google/filament/issues/7151