It wasn't "free" stock. An employer's contribution to a 401k is compensation for one's labor. So the Enron employees personally earned that stock.
In other words, they lost that part of their compensation, which they were never free to invest as they please. I call that a bum deal.
I don't know anyone who receives company stock for the employer contribution who has to hold that stock until age 50 regardless of whether they leave the company.
One's salary is one's compensation for one's labor.
Stock awards are a perk.
No employer is required to provide matching funds or stock awards with a 401k plan, and any employer can choose to discontinue such stock awards or matching funds at any time.
Employers cannot by law choose to discontinue compensating employees for work performed, so clearly matching funds and stock awards are not compensation since 401k-providing employers can discontinue them at any time without penalty or liability.