Abspos Multicol With Spanner Becomes Spanner Expected

We have a multicol with an absolutely positioned multicol child. That child has a spanner inside. The absolutely positioned multicol child isn't part of its parent multicol, since it's out of flow. The absolutely positioned multicol also has column-span:all, but it doesn't apply, since it's out of flow. Now make it statically positioned. That will turn it into a spanner in the parent multicol. At the same time, change it from multicol to regular block. It will still be a spanner, but since it's no longer multicol, its child spanner can no longer be one, since you cannot nest spanners in the same multicol context. So you end up with a multicol with a spanner with a regular (invalid spanner) block.

Below there should be four squares stacked vertically, in the following order: hotpink, yellow, papayawhip, olive.