Yes, this is true. And they have practically no security compared to the Capitol. Though I have to say, once you get through the visitor center, the Capitol isn't really locked down very tightly, especially off-season.
One thing that's fun to do in DC, if you plan ahead, is get a White House tour. Sadly they don't let you see any of the west wing, but the rest is still pretty interesting, and the Secret Service agents are really cool. We had some really great conversations, they're extremely knowledgeable (and proud of it, too). I asked one of them how many steps he thought I could make it if I jumped the rope and headed for the staircase up to the residence, and he just chuckled. Funny thing is he'd probably not even bother tackling my fat ass, he'd just grab my arm and escort me out of the building. They were pretty proud of that, too -- the discipline they have and ability to use just enough force without going over the top. I was impressed with their professionalism. Not that it should be surprising, presidential protection is an elite detail.