Rogier,
First, I'm not going to get into the way some proposals duplicate other sites and proposals, because two wrongs don't make a right. If you want to ask about particular overlaps, there's a better place for that discussion.
Yes, it is true that there are currently no Advanced Squad Leader questions on Board & Card Games. But BCG has plenty of questions about war gamesplenty of questions about war games, and based on the discussions on BCG's Meta, they're fine with getting more.
Just to make sure, though, I've opened a new question there, Are wargame questions welcome?, which asks about ASL in particular.
If they agree that your ASL questions are welcome, try asking a few!