I'm reminded of many years ago, a coworker coming into my office and asking me a question about the design of a feature that interacts with our tax calculation.

So she and I created this whole whiteboard flowchart working out the design, at the end of which I said "Hrm. So, at a high level, this seems OK. That said, you should definitely talk to Mark about this, because Mark knows a lot more about the tax code than I do, and he might see problems I missed. For example, Mark will probably notice that this bit here will fail when $condition applies, which I... um... completely failed to notice?"

I could certainly describe that as having a "Mark" in my head who is smarter about tax-code-related designs than I am, and there's nothing intrinsically wrong with describing it that way if that makes me more comfortable or provides some other benefit.

But "Mark" in this case would just be pointing to a subset of "Dave", just as "Dave's fantasies about aliens" does.