If they were worried about server admins correlating Apple's IP addresses with a new User-Agent string, the team could have VPN'd to a non-Apple network to access the web.
I guess they were worried both about having recognizable IP addresses AND having the name of their new browser appear in logs all around the world.
The user agent was something like "Mozilla/5.0 (Macintosh; U; PPC Mac OS X; sv-se) AppleWebKit/85.7 (KHTML, like Gecko) Safari/85.5", which people would have quickly correlated to Apple, not matter what IP it came from.
The string was originally just contained "WebKit." When it became "AppleWebKit" in mid-December (as I recall) then, yes, it was more likely to be discovered. But I felt that a 17.x.x.x address would be the clincher and the secret would be out.
The user agent was something like "Mozilla/5.0 (Macintosh; U; PPC Mac OS X; sv-se) AppleWebKit/85.7 (KHTML, like Gecko) Safari/85.5", which people would have quickly correlated to Apple, not matter what IP it came from.