As soon as another team scores first we we struggle, and 4/5 have scored against us so hardly a time to claim invincibility.
Not sure if anyone's claiming we're invincible, but that's a valid point you raise. We're yet to go behind under Guardiola, so it'll be interesting to see how we react when that happens. Historically we've struggled when conceding first - I'm sure there's a ridiculous stat about us not winning games when we've trailed at half-time? This team feels different though, but time will tell.
For me, one of the biggest challenges facing Guardiola is Liverpool away (and to a slightly lesser extent Arsenal). We seem to always go to those grounds already beaten, and have lacked the mental fortitude to grind out results there in the past. It would be a huge statement if we could win those games.