Even though the original post is from 2019, it is good to see people are still making comments on what is a serious issue.
As has been said by many, there is no "legally defined" height and the common "norm" when training is generally the forks between 4 - 6 inches from the ground and tilted backwards.
Here in the UK, it is one of the questions you can be asked as part of the Theory Test:
When driving an unladen lift truck how should the forks be set?
The answer is: As low as practicable and tilted back
But as many have said, it comes down to the initial training and then the management on-site to enforce good practice.