Details of the nature of the problem are still withheld. We asked for more information on Tuesday morning and once again their poor put-upon PR team had to come back to us at the end of the day saying that they would get back to us when they could.
In other words, Microsoft had told them to say nothing, which for a corporation that has made repeated claims that it was going to be 'more open' is ridiculous and goes some way to explaining why we don't bother waiting for comment from them anymore - we'd never get anything done.
We've been referring to this update as the "Spring Creators Update" in lieu of anything official, but it does seem that even this is still open to debate, which is odd within itself.
Right now, it looks like we probably won't see a rollout in the stable channel for another couple of weeks, so you'll have to hang on until then, and then for the several weeks or months, it usually takes to roll out completely.