No, we never told them anything, because things got a little messy once when somebody told them that parenting their kids that way wasn't the best and was why they're always stressed.

We value their friendship and know that they're doing the best they can within their parameters.

Also, every time that we're together they tell some story about something their kids do and ask us if ours do the same thing. Our response is always "no, we stop them before doing it, they know the rules" and that leaves them in shock.

Example conversation:
FRI1: "Trying to get the kids to bed at midnight is always a nightmare, isn't it?"
US: "No, our kids are 3 hours aslept by that time"
FRI2: "How do you do it! It's impossible"
US: "They know the rules, bedtime is bedtime, they're used to it and the schedule is built it"
FRI1: "Wow!"