Do I need to use CustomBlending with premultipliedAlpha texture？

Questions
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1

Suppose that the texture has been multiplied alpha by the artist, I should use gl.blendFuncSeparate( gl.ONE, gl.ONE_MINUS_SRC_ALPHA, gl.ONE, gl.ONE_MINUS_SRC_ALPHA ), right?

But the default setting of threejs(Texture.premultiplyAlpha: false; Material.premultipliedAlpha: false Material.Blending: NormalBlending) will lead to gl.blendFuncSeparate( gl.SRC_ALPHA, gl.ONE_MINUS_SRC_ALPHA, gl.ONE, gl.ONE_MINUS_SRC_ALPHA ).

So I should use CustomBlending？