Leicester has a little more margin, but I think pretty much everyone can agree they're playing above their heads now and it shouldn't be expected for them to keep this up for an entire season.
I don't think Leicester are playing above their heads - consider their list of victories one by one:
Sheffield United (away), Bournemouth (home), late-stage Pochettino Spurs (home), Newcastle (home), Burnley (home), Southampton (away), Palace (home), late-stage Emery Arsenal (home), Brighton (away), late-stage Silva Everton (home), Watford (home)
There aren't many eye-popping results there, rather a good team consistently playing at the peak of its potential, suffering few injuries, polishing off more or less anything that crosses its way that gives off a hint of mediocrity or vulnerability.
The lesson of 2015/16 was: beat the dross, and holding your own against the big six is sufficient to challenge for the title if the big six all falter. Remember Leicester's record that season:
Versus the big six: played 12, won 4, drawn 5, lost 3, points 17
Versus the rest: played 26, won 19, drawn 7, lost 0, points 64
In comparison, by my calculations runners-up Arsenal took 18 points from their five traditional rivals plus Leicester, and 53 points from the rest.
Spurs' breakdown was 16/54, The People's Billionaires 9/57, The Fallen Empire 20/46, Liverpool 17/43, Chelsea 12/38
As with that campaign Leicester has so far stayed healthy, a factor which can hardly be counted upon over the rest of the season.
In 2015/16 Ranieri made them more defensive roughly halfway through the season. We'll see whether Rodgers has any adjustments up his sleeve if opponents turn out to have spotted weaknesses that they target when all the teams play each other a second time.
Manifestly, the great obstacle Leicester face is that up to this point, 2019/20 Liverpool is a far superior points-gathering machine to any of the established contenders of four years ago.