Talk:Type Qualifier (GLSL)
The note about precision qualifiers being specific to OpenGL ES 2.0 only and has no functional effect does not appear to be true. If you read this OpenGL ES 3.0 Quick Reference on page 5 section 4.5 it shows that they do exist. In practice I have seen the qualifiers function on Android 8 Tablets specifically. Another words, when the precision highp qualifier is present the results are different when the precision highp qualifier is not present.