It certainly did happen. I think it's a bit different though, as there was a hell lot of talk after the Arsenal game that both Arsenal and Liverpool would win their last 9.
Even with the incredible points totals that have been posted recently, it's pretty unusual. Liverpool and City did it in one season, but has any other team ever won their last nine games? Even that Liverpool season, they had a fairly relaxed easy run, with their toughest away game against the team that finished 13th. The reason we won that year is that they'd just dropped points at United and Everton.
For it to happen in a season where the top three are all having ok, but not great seasons, where their records against other top six sides are poor, and where there are still plenty of clashes with top six sides, it felt really unlikely.
Obviously Liverpool fell at the first tough test, and I'd be really surprised if Arsenal didn't drop points.