There's always an exception that proves the rule. I'm sure, though, if you could provide an explanation like this and then provide and walk them through some already-written code examples, that would also be acceptable?
I'd take someone who says "I can't live-code while talking about it, but here's an example of my code and I can explain how it works" over someone who tries to BS me.
Yep, I can do what you suggest, and I've done it before. It can go a little sideways, though, depending on the questions you ask. If your question requires me to do what I can't do in an interview setting, then neither you nor I will be happy with the result.
Don't get me wrong; you as an interviewer are not under any obligation to adapt your hiring process to my quirks.
On the other hand, I'm not under any obligation to participate in a hiring process I don't like, either. I stopped participating in hiring processes I don't like around two decades ago, and I've survived anyway.
I'd take someone who says "I can't live-code while talking about it, but here's an example of my code and I can explain how it works" over someone who tries to BS me.