You can rebuild them, you just cannot remove the levels.
Let's say you've been a 18 RDD 2 Sorcerer 10 fighter. You can still DC or self rebuild into a 18 RDD 12 bard. (These are examples, pelase do not judge the power quality of these builds now
) and change skillpoints, feats, abilities. It simply means you cannot (at such high RDD progression) simply not be a RDD anymore and rebuild into a 16 WM, 2 Rogue, 12 fighter, or even a 4 RDD 16 WM 10 rogue.If you just want to loose a level or two of those classes (like from 18 RDD to 16 or somesuch) the case will be judged individually and we can see about that.
You cannot anymore however go from 16 PM (or RDD) to 0.
And correct, this isn't really anything "new" it has been mentioned a few times already in between discussions and requests and so on.
However, I know the playerbase (rightfully) struggles to sometimes find rules as they have just been mentioned a few times and "assumed everyone knows" and then there is big confusion if people didn't know. As a self-discipline for 2017, I am trying to make this a bit easier for us all and just make it easier to find. Ideally, I will try to re-work the whole "rules" section eventually, which seems rather lacking. To put it mildly.