I can imagine this working, but digging into it at the time, there was no validation it worked at all. I couldn't get videos of it working, or even a cogent response from the author.
One of the things people seem to miss, is that bring intelligent doesn't mean domesticated. Or that an animal domesticates well.
Crows can understand a great deal, but does that mean they care to do your bidding? Even for treats?
Take a look at the differences between cats and dogs. You can train cats, but often they barely care. Dogs are, however, far easier to train.
Likely a difference in external validation.
And after all, what is true value to a crow? City crows seem to have an easy time of it. I don't think they go hungry, and there is lots of free tasty food.
So why would they care?
It's pretty cute how disappointed they can look when they realize you just threw a peanut.
Again cats are harder to train than dogs, and that's with treat enticement too. Yet they will certainly make a face when given lesser food.
Also, keep an eye out for one crow watching for you to appear with treats. Once you do, he'll call the rest of the tribe.
I noticed a ypunger crow doing this. Unclear if it was assigned the task as a junior, or did so for street cred.
Adults were busy at this time of year showing juveniles how to find food and such.