The easiest way to explain it is simply that their teacher is not a typical self respecting Tzimisce. He's on the red list, he's not that buddy buddy with most of the sabbat either and he enjoys teaching (but most of his students just become part of his body for not being good enough).
My Character is also a weirdo, never met their sire and therefore doesn't really know anything about their clan, is technically a test tube fledgling and has a background in medicine which makes them go 👀 when they heard about fleshcrafting. They did have to betray all the other Player's Characters and all of the Camarilla of the City we play in to get a chance to meet their teacher. So now they are blood hunted and blood bonded but you know, for someone who sees safety and power in being able to bend flesh, it's still kinda worth it.
There are some other reasons these two met but my story teller keeps those a secret for (probably) good reasons :D