Yes, as in yes mine is the same way. And if you look carefully you can see a ridge down there.. maybe use a flashlight.
I used a 400mm post with no problem. Yeah i couldn't put it ALL the way down, but PLENTY low enough for any kind of aggressive riding.. even too low for real DHing. Anyone big enough to be riding a large frame certainly doesn't need to slam the seat all the way down that 17.5" seat tube.
But yeah.. kinda ridiculous nonetheless.