Pretty much every dog trainer in the world will tell you different dogs are motivated to different degrees by different things. Very weird point to argue on.

I have two purebred poodles (not bred for Instagram) and one is highly motivated by food, the other will decline treats pretty often, even treats we know he really loves. This is not super atypical of poodles.

And to put another layer of complication on your dismissal of other people's challenges training dogs: the not food-motivated one is way easier to train.