I'm sorry, but what are you talking about? The carrilero isn't hard coded for anything, but stay wide and not roam or hold position. In fact, he will be as cautious as a CM on support when you change mentality (fm22), like any other role on support in the midfield.
I would like to know where did you come up with that definition of "generic role", because it doesn't make any sense. It's like you are mixing generic roles, support and automatic setting from the CM role all in one definition. The generic role means the role can be tinkered to do a lot of different things, is a blank canvas, nothing more than that.
Anw, talking about the carrilero in normal width systems, I really think it makes more sense than the way people try to imitate guys like Xavi and etc using mezzalas on support.