Look, if you want to talk about code, the easiest and best way to sidestep this issue is to have people bring code (somewhere between 200-1000 lines) to the interview. While they may not have a github presence, they've probably written something on a computer outside of business at some point.

I really don't understand why more people don't do this.

It doesn't even matter if it is their own code. The fact that they will have to talk intelligently about it means that it will accomplish its task.

I used to get this issue interviewing with VLSI chip companies all the time. "Do you know Perl?"--"Yes, I do, but I don't know YOUR particular favorite subset of that write-only language" doesn't go over well in interviews.

After getting tired of getting dinged on questions about a language that I had used for almost daily for 5 years and that I abandoned for good reason, I took an old program of mine from Python and ported it to Perl. I bring both.

Now, I have something concrete to talk about, can actually compare the points of two languages, and most interviewers realize that "Gee, you're probably better at this than I am."

This shifts the conversation from "Technical Jeopardy!" to "Ah, you know how to program, let's look.", "I did this. Here's why.", "Oh, that's interesting. What does that do?", etc.