Taking a format that only a computer can interpret, code, and choosing to write it down on a medium a computer can't read, hand-writing, is not typically a productive exercise.
Even in interviews I'd rather hand a candidate a laptop.
There are more worthwhile things to hand-write, such as sequence diagrams, and there are more worthwhile places to write code, such as an IDE.
If someone is finding it easier to write code on paper than in an IDE, I'd rather not ignore that signal and try to discover why their IDE is proving such an impediment.
Maybe it takes 10 minutes to start up, maybe it throws up so many errors for each syntax mistake that it's distracting and hard to see the wood for the trees. Maybe it doesn't actually produce useful output. Maybe it doesn't have real time debugging and step-through.
Who knows, but something is causing it to be mentally easier to write down the same code on paper than the IDE, and that's not something that should be ignored, that's something that should be fixed.