Besides a dice that's as even as possible, the other requirement this solution attempts to satisfy is using the minimum number of cuts. A blender doesn't satisfy that, as it's making hundreds of cuts.

Then, when you present your solution to the client, you find out there was a third, unspoken requirement: that it should involve as little cleanup as possible, which the blender also doesn't satisfy. The user researcher was on vacation, and you didn't find out about this before beginning design. Damn!

The blender solution turns out to be overoptimized on a single requirement at the expense of the others.

They're optimizing for time as knife cuts = time. A food processor will do it faster if you're more than one onion or so, assuming you can get the size you want.