Basically yes.
You can't change classes until you have five advances. Simplifying slightly you pick your advances from a list of about a dozen (it varies slightly by class) and on that list are two options of any move for your class you haven't already taken, two options for any move from any other class, three to five advances to a stat (depending on your class; some are more flexible than others) and often a couple of extras - class specific although frequently . And switching classes takes the place of an advance.
So if you start off as a member of one class and want to transfer to another it's entirely possible that every single advance you make before you change classes is either a move from the class you are going to transfer to or a stat boost. Alternatively it's possible to change classes without mechanical preparation if for example you get some sort of windfall or just decide as a hardholder you've had enough, and want to just be a gun for hire.