I’ve never seen this actually applied to or even talked about with engineers because it’s absurd. What software engineer is directly selling to customers? Is there somewhere that has had them enforced?
I think the comment you mentioned might talk about non-solicitation in the sense that the former employee of company A who's now working for company B can not solicit the remaining employees of A to work for B?
Funny enough, I helped plenty of people from past employers to find new jobs; but never with my current employer, but typically with some other past employer.
I was talking about all the consulting engineering firms full of civil, mechanical, electrical, transportation, etc, engineers. Among these jokers, it's extremely common practice. As a side note, in Ontario 'engineer' is a protected title and most (but not all) programming jobs wouldn't qualify.
But since this is a US website about programming/business, you're probably not going to talk to a lot of Ontarians about programming or engineering, so this is probably useless information for you. But hey, there you go. Trivia night.