I noticed the same when I was trying to find a site up there. Note this is not the "Hanscom AFB Famcamp" as the title suggests. Fourth Cliff is a completely separate facility between Boston and Cape Cod. The website for the main Famcamp located on base is
(scroll down to Famcamp). Hanscom FSS also runs the New Boston recreation area in New Hampshire
You probably know all this, but I'm adding it in case it helps anyone else. I was initially confused about which campground I was checking out. I couldn't get a site anywhere up there and wound up in NJ instead. Maybe in September we'll get up to MA and beyond.