I don't think they'd do something like that willingly. A likely guess is it's something related to the framework they're using on Cloud Manager (to make cross platform easier) and that being tied into Chromium. If there's a security flaw identified, and they can't update things easily for some reason, then they'd be in a position where they either ignore it or pass the authentication stage off to the external browser (to remain secure) until they fix it.
Not saying that's the reason btw.. Just that it potentially "fits" with what we've seen. There might well be some alternative reasoning. But the jump out of the Manager program is a bit jarring, especially if you're not expecting it.
