In https://immersive-web.github.io/layers/#allocate-color-textures-for-projection-layers, the algorithm for allocating textures for projection layers says "Let numViews be the number of the session’s list of views..." and allocates that many textures. But over in https://immersive-web.github.io/webxr/#update-the-viewports, there is text for "When the list of views changes", which implies the list of views may change over time.