This is quite issue with texture filtering, none of the available filters in Bitmap and CoronaBitmap preserve details well unless you are rendering in really high-resolution (of framebuffer).
You can set most of your textures to "None" and 0.01, but this will create issues in many instances (particularly Normal and Bump mapping which require certain level of filtering). Other issue is that may just create artifacts (or just pure noise) instead of correct detail like when rendered up-close (or in high-res).
This is issue that makes many people, including me, very unhappy for many years and I don't think there is any solution right now outside of always rendering very high-res even if you down-sample afterwards for clients.
When you render 4x bigger (8k instead of 4k), you can use higher noise threshold since the noise will vanish after downsampling. So rendering higher-res doesn't necessarily mean higher-render time in linear fashion.
Your example (Anisotropic details of metal) are particularly the most glaring issue with this right now. With well filtered detail of texture, your metals would be perfectly brushed and anisotropic automatically, with no need for setting any roughness or anisotropy.