Your breeder, if they said that, was speaking in 'certainties' in an uncertain situation.
Puppies should never be left to cry. Why? Because if you return when they are crying, they take their crying to have encouraged your return - i.e, they will likely cry more in the future to encourage you to return. Not only that, puppies can and do panic - and cause catastrophic injuries to themselves in the process (including in one case I know, dislocating their jaw). Verbal reassurance does literally nothing in those early days unless it is accompanies by something physical. Why? Because the puppy doesn't know you at all.
You wouldn't train a puppy to sit by yelling 'sit' at them, would you? No. You'd do the hand signals and luring first, then tack on the sit and then, eventually, the dog would learn to sit by itself with just the command. Building a relationship with your dog works in much the same way as training does - body signals, physical movement (and comfort) first, and then words later.
And showing affection to an eight week old puppy that has been taken away from everything it has ever known only does one thing - to build a bond between them and their new owner.
Honestly, your breeder sounds like a bit of a nitwit for giving that advice. Advice like that is more likely to cause dogs to behaviour in nervous ways and/or increase chances of separation anxiety. Particularly if it is taken as 'certainty' rather than 'in X or Y situation.'