You don't know that, in fact not so long ago you were saying Whithouse was a shoe-in to get the job. He's written eps in every Moffat series after all? Chibnell hasn't.
He's written two episodes this year, was supposed to write three
and "Pond Life" too. He's been allowed to cover the big character stuff that RTD or Moffat would normally do themselves. It's hard not see him as being groomed for the Big Seat.
Or you could say he's covered the big character stuff of the characters who aren't going to be around much longer?
Oh well, guess we'll see when it finally happens. Do you know exactly when Moffat is leaving as well?
In-story, it's not so egregious. Looking at it from the writer's perspective though, it's clear to me RTD had a better handle on what to do with his female characters than Moffat does.
Personally I wasn't overly happy with the endings RTD gave any of his era's companions. I found them shallow. Rose settling for second best with fake dad and fake Doctor, Martha giving up her career and fiance to be a mercenary with Mickey? And as for Donna...what he's saying is, it doesn't matter if you lose everything that makes you special, just so long as you're rich. Amy may be floating around a bit aimless, but at least she's doing things off her own bat, a far better example to set than the others.
Just my tuppence worth or course