kmontrose of StackOverflow informed me in his comment that this in fact was not their intention at all. Futhermore, they don't use any of their user's Facebook

kmontrose of StackOverflow informed me in his comment that this in fact was not their intention at all. Futhermore, they don't use any of their user's Facebook profile data. I now realize it was a bit of a stretch to say that Stack Overflow engineered their UX in this manner. Regardless, the strong password requirement DID convince me to sign in using my Facebook credentials, and I'm sure it will convince others as well. In conclusion, I think a very strong password could actually funnel users into signing in with 3rd party credentials.