Can scissor be used to render twice to different halves of the same texture?

This works when screen is the render target (Webgl1Rrenderer) for rendering stereo, but does it work when the render target is a texture?
While I haven’t managed to make this work, I can’t find any documentation that states or implies that it cannot be done.
This could eliminate the 3d pass (left cam to a texture, right cam to another texture, then read both and combine them to a third texture).