Having the actual documents makes a huge practical difference. In the absence of the documents, the employee's new company basically has to re-do the research under the employee's guidance.
Some will disagree because there exist people who can memorize everything.
Or you are saying that a person can't create a plan to be followed by people below him?
It would be a life's work for anyone to memorize 600kb text only file.
He wouldn't have been okay. In most states, trade secrets don't have to be contained in a document or other recording. If you memorize the formula to Coca-Cola, it is still a trade secret. The dividing line between skill/experience/general-knowledge and a trade secret is fuzzy.
Though, its a lot harder to win a trade secret case when the alleged trade secret is only in the mind of the defendant because it's harder to show that you misappropriated it.
Somebody will inevitably reply that I'm wrong, and then I'll still travel slightly over the speed limit with no consequences for ~5 hours today.
See https://en.wikipedia.org/wiki/Bright-line_rule for a starting place to learn more about this.
The discretion police use is a huge gray area that is often problematic, but probably less problematic than not having a gray area.