The manufacturer doesn't know anything about this that isn't public information.

Yes, two doses are almost certainly better than one. But those are not the choices.

When there are far fewer doses than the number of people to vaccinate, the question is if it's better to give N people 2 shots, or 2N people 1 shot.

The test data looks like 1 dose gives ~80% protection vs ~95% for 2 doses. The 2x80% scenario is clearly better than 1x95%.

And, of course, everyone would get the second dose as soon as production catches up.