Veal Stock-Cleaning the bones

Can anyone help clarify exactly what one is supposed to clean when rinsing veal bones after blanching them for white veal stock? Some recipes make it sound like you just wanna rinse the gunk off them...while others make it sound like you are supposed to scrub them ENTIRELY clean of all the excess meat, fat, tendons etc until they are simply the bones and nothing else. Are we supposed to clean even the marrow out?

I get the difference between a broth flavored with meat and the flavor you get simply from a bone broth...but I'm just trying to understand in a very classical way, whether the layer of rough stuff attached to bones or the marrow inside them is part of what makes a classic stock, or if that leads to 'impurities'. I have been removing it all and I am worried that I'm idiotically killing all my flavor.

Thanks!!!