In IT, development, there are often a lot of different ways to achieve a thing. Version control is one of them, for most basic needs most version control systems offer the same features. Subsversion, mercurial and git? I can use any of them and have all common needs met. So why demand specific knowledge of a specific solution?
Because of shit for brains developers. They are ALWAYS on the lookout for the magic tool that means they don't have to do their job anymore and insist solution X is the only solution until a new flavor of the day comes along.
Here is a warning sign, if your a web developer and the job/project uses more then two programming languages, RUN! It means the developers are hammering in their flavors of the day creating a mass of code in different languages, 9 times out of 10 completely depended on a specific config and version that nobody wants to bother with anymore because their experiment failed and now they want to experiment some more.
Interviewing is like dating, its main goal is NOT to find true love but to ditch the crazies before they found out where you life (but I will get you my pretty oh, yes and then we will be happy FOREVER) anyway, if a job seems to suck during the recruitment process consider yourself warned and move on (but I will never let you escape!)