I'll go with "both right"
I don't deny mutual chemistry. The article I was reading was talking specifically about those people -- and I know several -- who will walk past the cute, friendly puppy in the first cage because "I'm sure someone will take him," going instead for the "problem child" near the back. And they tell themselves they're doing a good deed for an animal who needs it. And the pound employees then put down the "good" dog because no, after all no one did take him.
I'd never question the connection you had with Sierra. I'm just saying don't go out of your way to find an older cat because they're "more in need". The younger ones (but past kitten stage) are just as much in need.
But yes, trying to apply logic to something like this is probably questionable.
