That's van Flandern's radical proposal. Nothing adds up, mass, orbits, composition, time schedule. We may never know. If we did know, it would be one of the few things we actually know.
There has to be an explanation of the fact that it is plastered on one side, though. It was close to a planet-size or at least a large-moon-size object that disintegrated. If it weren't for that then this would be a radical theory because there wouldn't be much evidence. I think it's more radical to ignore this plastering than to consider a theory that explains it.