Yeah, the compendium shows it as being updated in the Class Compendium, so I went to the Weaponmaster article. The new version is in the pages from the Class Compendium, but not in the updates file. So in a way this is stealth errata.
It seems to me that wizards has decided they don't need to release errata documents for things that get updated in print products, as we saw in the Dm's kit, or updates from the Class Compendium, which was supposed to be in print, and is now available free on the website.
This has always been the policy, it's just come up very rarely before now. I think the best known example is the reliable keyword: after PHB it received one update via the errata process, but then it received another eupdate in PHBII. The end result is, the keyword is defined in one way in the official errata, but because it's errata for a book that comes before another, the errata is overuled by the printed PHBII.
This has only recently becomre really problematic. The rules compendium contained dozens of rules updates which will never be free online. That entire book is effectively "Errata you pay for" and nothing else.