I don't think it is stretching it and a quick look at previous managers shows that his PPG is up there with the best and better than many. John Hughes in 2014/15 is the last time we saw it that high and only in promotion seasons prior was it higher.
I've deliberately not mentioned other factors in this (but others have) because it's tough to quantify and whilst we can't judge his ability to put a squad together etc., we are seeing his ability to get much more out of a squad than his predecessor and many other 'good' managers in our history.
Not denying there hasn't been disappointing performances and results in there too but that's part of football and judging managers on individual games and not overall results during their tenure is a slippery slope.
I think he's already delivered the near impossible by going into the last 3 games with hope of league survival. When he delivers it that will be the miracle.
I'd be really disappointed if Kell was removed at the end of the season and think it would be unjust.
Weirdly I think he'd be getting less criticism if we hadn't got anywhere near 8th place because people's expectations wouldn't have been raised so high.
The ultimate case of being the victim of your own success?