I'd think it isn't about employee getting 30%. It is about the companies would be paying money really for nothing in most cases, and thus forcing the companies to avoid blanket enforcement (and unpredictable at that as it avoids the company having the free option of coming after you nilly-vanilla when they feel like it years later) - and such avoidment is great for innovation industry-wise. If your confidentiality agreement is really meaningful, then probably you can negotiate much better payment.

I believe this is the interpretation that most closely reflects the intent of the legislation. This is not a form of income, but rather a means of discouraging companies from acting recklessly.