Plenty of people run cracked VF* turbos and they hold boost fine. Still though, this is far from perfect, I'd be pissed for seller not mentioning the crack -- it's pretty big, he'd be blind (like, "not allowed to drive legally" blind) not to notice it.
really! is up with Impreza peeps not selling stuff as advertised lately? Bad enough they don't wave.. Lamerz.
It sucks that they didnt mention it in the ad, but it will be fine regardless. It takes a BAAAD crack (as in chunks of material missing at the sealing surface of the flapper) to cause problems. You could see 100 cracked turbos and you MIGHT see 1 that has performance issues caused by it.