If it's what dad's doing because he knows it's the right thing, and the family is along for the ride, that's not OK. And I've seen that dynamic a lot.
Sounds like it doesn't describe you at all. And there are definitely guys who use "family time" as an excuse to be lazy. But that doesn't mean that everyone who chooses to keep their hours around 40 a week when their kids are young is a misguided slacker who's doing it wrong. I don't think you mean that, but you sometimes come across that way.