By including features in the manual. The alternative is that they don't, people rely on the features, they change the features without notifying anyone, and when shit goes wrong they can say "It wasn't documented: shouldn't do that".
The real question here is how commonly this feature was used. If it was common, then not putting it in the manual is a big problem!
The real question here is how commonly this feature was used. If it was common, then not putting it in the manual is a big problem!