If they decide to start enforcing the return times I think we will know ahead of time. When they did it in WDW, they announced it to various Disney fan sites and then posted signs at all the fastpass entrances about a month before they started the enforcement. I would imagine they would do something similar in DL if they decide to do this.
This also could be a simple matter of which CM's are on duty at the time. Even though company policies are in place that doesn't mean the employees are enforcing them. Disney could have told the CM's to enforce them and maybe only a few are and the majority still aren't.
It's like if you go shopping and pay with a credit card. Technically the cashiers are supposed to look at your card and match the name with your ID. How many cashiers actually do it? Very few. I almost never have to do that when I buy something anywhere.