Yes, it seems to be a good theory, supportable by evidence, rather than merely a vague hypothesis - if one makes the assumption that the solar wind had not already removed most of the hydrogen from the inner Solar System.

The voids you speak of could have been large and numerous during the earlier stages of accretion, when gravity, and therefore compaction, was low. It's not difficult to imagine that much of the trapped hydrogen had sufficient time to combine with oxygen before the remainder was forced to the surface.

"Time is what prevents everything from happening at once" - John Wheeler