They also didn't just wake up one day and decide to play this way. They've been working on it since preseason.
Not necessarily purely formation. But they were certainly trying a more fluid positioning during a couple of preseason games that I saw. This is imitate to the 'total football' everyone is talking about now. It looked horrible and messy during preseason (though they still beat Miramar 9-0 etc) but it looked good on Thursday. It'll be interesting to see how we go against a stronger side, I remember during preseason thinking they must be trying sometng new and that if we play like that during the season, we'll get ripped to shreds.
I genuinely think this is something they've been working on all season, rather than something Gareth dreamt up one night a few weeks ago and told ricki to adopt immediately.