eaglercraft-1.8/sources/resources/assets/eagler/glsl/deferred/assets_pbr/readme.txt

these are just low quality fallback material textures for the default vanilla resource pack when no PBR resource pack is loaded, if you would like to make a PBR resource pack put your _n and _s textures in the "/assets/minecraft/textures/" directory of your zip file, do not modify any files within "/assets/eagler/glsl/deferred/assets_pbr/textures/" because they will not be recognized