Steps to reproduce:

1. Open attached project (RenderTextureTest_stripped.zip)
2. Make sure graphics API for iOS is set to Metal
3. Build the project for iOS and open it in Xcode
4. Go to Product/Scheme/Edit Scheme and change 'GPU Frame Capture' in 'Options' tab to Metal
5. Run on a metal device
6. Make a GPU frame capture, click on FPS tab and see the GPU frame time
7. Set graphics API to OpenGLES3
8. Build the project for iOS and open it in Xcode
9. Run on the same device
10. Make a GPU frame capture again, click on FPS tab and see the GPU frame time - notice it is smaller compared to Metal build

The results differ depending on a device, but Metal always shows slower GPU frame time.