Why render target texture is wrong

When I render to target I change model color to red. Model material is MeshPhongMaterial. I have one scene and one PerspectiveCamera.
Why render target texture is bad?

renderTarget = new THREE.WebGLRenderTarget(
200, 200
          depthBuffer: false,
          stencilBuffer: false,
     renderer.setRenderTarget(renderTarget );
     renderer.render(scene, camera);

Left up corner present canvas2d draw image from readRenderTargetPixels
Beside scene is plane with material set map from texture render target.

2021-09-01 13_32_21-Window


When I run render to render target I change uniform that control color of fragment.

My target goal is that render target must be clear red color without black and others pixels.