I agree with this, and will vote for Corbyn because of it. I also don't expect to see another Labour majority government in my lifetime (I'm 60). There is not likely during that period to be a majority of the population (certainly now that Scotland has been lost to the SNP) who hold the same...
Presumably that's because he's not 17 points ahead on the second ballot (after redistribution of the others' second preferences), but only 2 points ahead.