I would agree with that statement. My understanding is that whenever anyone has gone to challenge this provision in court, the government has always settled. The DOJ has always settled.
The presumption in the immigration bar is that they don't want a precedent. The government doesn't want a precedent whereby a court would say that the current rules are a violation of those obligations. What happens is that you include the parent on the application anyway; it's refused, and then you file a judicial review application and the government says, “Okay, we'll settle this. We'll let them be processed together.”
As I said, the assumption in the bar is that they don't want a precedent. The reasons you've raised are probably why they don't want a precedent.