Good point, and I follow your thinking.
To amend - waist isn't the first place for everyone, for some people it might be the last place where excess weight is gained! Most clear example of this is the sexes in the age range 30-40; men of this age will likely put in visceral (intra-abdominal cavity) fat and women the thighs and hips -- even so this is just a trend. For me, cheeks followed by thighs are one of the last places to go.

But again - good point, this may well be something to be expected (as well as those who are losing weight at first gaining muscle and actually increasing weight/size fractionally before losing it at the start of their new lifestyle due to muscle response and growth as a result of the exercise they are unaccustomed to). And also temporary fluctuations that contribute to everyone due to hydration, salt levels and various other minor factors. :p
Oh ok, I thought most people store the fat around the waist, but obviously this depends. For example I definitely store fat there, and also the face.
So basically anyone that has gone past the newbie gains and is able to lose fat way faster than put on new muscle might be thinking that as they lose weight they in fact look worse, since the analogies change mostly depending on fat storing areas.
Perhaps that is a good reason to take it easy with fat loss, so it almost matches muscle gain, so the analogies are kept roughly the same.