You know because they aren't competitors or anything silly like that.
I think it's pretty clear one of the primary drivers behind Google+ is to reduce the amount of time users spend on Facebook and transfer it back to Google. The new 'Events' features are a good example of this.
The only reason Google aren't going around saying they're going to 'kill Facebook' is that it's only going to result in inevitable embarrassment. What Google PR says and how they develop their product strategies internally are very different things.
The point is, G+ was never billed as a facebook killer. The OP who stated that is reiterating the media talking points (and pretending these are the words of Google execs). Vic's message has been consistent and concise. Does some G+ features overlap with FB? Sure, but the stated goal was never to build a facebook killer.