He's supposed to be. He was born at Prague in 2007 and came to Chester in 2009 as a breeding male although as you say he doesn't look like a typical Sumatran (white "mane" around face, he's relativly small compared to a a pure Amur individual, and more stripes than you can count!) when I first saw him in the flesh I was also taken aback by how similar he appeared to an Amur youngster.
Just before this spins off into speculation - as far as I'm aware there has never been any suggestion that 'Fabi' is anything other than pure Sumatran.
Pure he may be... but he still doesn't look quite 'right' to me somehow...maybe he looks better in real life.
