Right now the specs for contain:paint and for transform-style allow an element with contain: paint to be part of a 3D scene. If such an element both has transform-style: preserve-3d and has a parent that does, then this means that its children (or further descendants, if the children have transform-style: preserve-3d) are rendered as part of its parent's (or further ancestor's, if the ancestor chain has transform-style: preserve-3d further up) 3D scene.

While the intended guarantees of contain: paint aren't clearly defined, it seems a bit nonintuitive to me that it would allow children to escape the container in this way.

What is the desired behavior here?